You can love someone, but not be "in love" with them. Divorce rates in the United States will tell you that people can enter into marriage and then learn it's not for them. I don't think any of them will tell you that they split because of demographics.
Peter Parker did. He stopped being married due to an editorial decision that was made to make him appeal to a larger demographic and, as much as it pains me to say it, Joe Quesada was right.
Give me a minute, that was hard to say.
Joe Quesada was right because an unmarried person will, in this day and age, appeal to a larger audience by pure numbers. Emotional attachments to characters and years of storytelling, continuity and respect aside, yeah. It's true. Spider-Man should fit in the "all ages" group that can entertain young and old, married and unmarried alike. Technically, more people can relate to being unmarried than being married. And while people have debated this technicality, the bottom line at the end of the day is Joe Quesada was and is editor-in-chief and was looking at a bigger picture than we, the fans. Quesada was looking at dollars, longevity and demographics. We just saw Peter Parker.
(WARNING: One Moment in Time Spoilers and Sadness inside. Grab a copy of Amazing Spider-Man #638 through #640 and read along! And then go visit CuteOverload because this isn't pretty.)
In order to take Peter back to a younger, less married point in time, an elaborate story was crafted. This was an event, the passing of old continuity to a Brand New Day (that's designed to evoke nostalgia for an even older continuity). In Marvel's "Civil War" storyline, Peter Parker unmasked himself and announced his secret identity; now knowing who he is thanks to having a TV, the Kingpin sends some assassins to ruin his civilian life. Aunt May is shot, and Peter is crushed that he brought this to his family. Then, Mephisto shows up and angers fans for years to come.
Now, let's get this one thing perfectly clear: Mephisto wants Peter and Mary Jane's LOVE.
The marriage thing is secondary (and has a more threatening font), but it's really just the representation of what he's going to get out of the deal: a heroic bond between man and wife. It's not like Mary Jane didn't know the job was dangerous when she took it or that it was ever perfectly safe during her tenure as Spider-Man's girl. It was her love for Peter Parker and her strength to see him through all the rough times that kept her from taking off, and that's what Mephisto wanted. You can take away a man's trophy but that doesn't take away the victory. So remember, when you later take Quesada to task at cons for engineering all of this, it was love and dedication that Mephisto wanted, not the cake or the dress.
You gotta give something to get something, so to take the Greatest Love of All, Mephisto offers another kind of love: protection. He'll save Aunt May's life if Peter gives up a part of himself. Mary Jane says she'll agree to this and ask Peter to give up their marriage if Mephisto just leaves Peter alone so, in a way, it's a little like the Gift of the Magi: both of them want to give up something of themselves to make everyone happy. The deal with the Devil Like Object goes down and the loss of Peter's love and stability causes a chain reaction in the Marvel Universes, altering many people's lives. We get a Brand New Day and Mary Jane fades into the subplot background.
Cut to a couple years later, and Brand New Day has lost its shine. It's less Brand New and more just a Day and sales slip. Joe Quesada gets asked constantly about One More Day and the great hullabaloo it inspired in fans. Technically, any publicity is good publicity and returning back to that story to try and re-refresh the title might do some good. Let's happily face facts: One More Day wasn't very good. It seemed forced, over-dramatic and was badly drawn in some places, and there are very obvious writing strains on the narrative. Joe Quesada had an idea for this story but it just didn't come through on paper, and he's taken to task for it all the time in front of crowds. Why not pump up some sales by revisiting the secret history of a major event and take a second chance on a story that honestly means a lot to Quesada. It was one of his "genies" he had to get back in the bottle, part of his wide-sweeping view of a leaner, meaner Marvel Universe, and it just didn't develop the way he wanted it to.
One Moment in Time is all about what actually caused Peter Parker and Mary Jane Watson not to be in love with each other any more. Mephisto didn't exactly wiggle his nose like an episode of Bewitched and *poof!* everything's different. In a "Butterfly Effect" style piece of work, Mephisto releases a criminal that Spider-Man puts away around the week of his wedding, and his release causes Peter Parker to get beat up on the day of his wedding. This causes him to miss it entirely, causes MJ to feel humiliated and angry, then sad and apologetic, then to want kids, and she asks Peter Parker to put down the mask. Peter can't do that, so they decide marriage might be a little too much considering his extreme lifestyle.
In a sad case of futility, Civil War still goes down, Peter Parker is still unmasked on TV, Kingpin still sends an assassin after him and Aunt May STILL gets shot. The doctors can't save her, but her nephew can and, in an act that can only be described as "love" by the hospital staff, Peter Parker sort of ... wills his aunt back to life. He gives her all his love because there is no wife to hold him back. He has nothing else in his life other than this sole relative, and he's able to dedicate everything to her for this miraculous act. While Aunt May recovers, MJ's Aunt Anna gets attacked because she's close to MJ, who's close to Peter Parker. There's a fight, innocent people are put in danger and Peter realizes that telling everyone who he is might have great consequences. So he heads down to Dr. Strange's and asks for a mind wipe of the populace.
Dr. Strange has to get the last vestiges of the Illuminati together (at this time, it's just him, Mr. Fantastic and Iron Man) and explain that it's going to take a combo of magic and science to really do this right. At the last minute, Peter pulls MJ from the big show so that she'll remember him because he needed her to be the only one who knew his terrible secrets. After all this is explained to her, MJ simply can't handle it. She feels like she's cursed just knowing Spider-Man and that all of her loved ones are in danger because of all this secret keeping. She doesn't want to live with the violence and threats and danger anymore; when Peter leaves to check on his aunt, she takes a cab and drives back off into the subplots again until she comes back to make Peter recall this whole story for closure.
Yeah, I almost wish Mephisto had just wiggled his nose.
These are two very selfish people; mind you, they're selfish out of love and some decent motivations, but in the end it's every Spidey character for themselves here. Peter forces the entire world into a do over so he can fix his mistake, pulls MJ out of that do over just so she can be the only one who knows the truth, he can't live with himself if anyone he loves gets hurt, saying "I did this for us" when Mary Jane seems near hysterical about the whole situation. He can fix all this, he can make it right and no one else gets a say in the matter. Mary Jane can't live with Peter's mask, she can't live with the shame of being stood up at the altar, she wants kids more than she loves Peter, she admits to not being strong enough to be Spider-Man's girl. She's no longer dedicated to her marriage or wants to give up anything of herself for a greater love. These aren't the same people from a few years ago. These characters have changed fundamentally by something originally (and I'm talking Amazing Spider-Man #21 originally) considered cosmetic. This is so much more than a marriage; it's the better part of two heroes.
At the end of Amazing Spider-Man #641, when we bring this whole mess to a close, Peter Parker hugs Mary Jane with the panel slowly nudging her out of the way to get to the guy on the cover of the book. "Today, my best friend, the best person I've ever known, set me free." He doesn't love her anymore. Peter wishes her the best, he cares very much for his best friend and would go to some pretty awesome splash page extremes for her, but this isn't a romance anymore. They'll never be that strong to look past themselves to see the greater whole again. No jetpacks, they do not have a future together anymore.