As much as the Team Rocket trio revels in being evil, they're not actually all that bad. Considering how often they've tried and failed to steal Pokémon, it's easy enough to write them off as harmless. If evil could be quantified, their net evil would have to be close to zero at the worst.
Not only is Team Rocket not bad, but they might actually be a little good for the world. Their actions throughout the Pokémon anime, however malicious the intent, have actually solved more problems than they created. For a better idea of how this can be, here's a look at some of their deeds and how they often resulted in a happy ending.
Obviously, there were plenty of times when Team Rocket was forced to act as begrudging allies to Ash and his friends. Sometimes, they'll have to work together to escape the sinking ship (Episode 16, "Pokémon Shipwreck"). Other times, they'll have to help out at a hospital and treat injured Pokémon (Episode 47, "A Chansey Operation"). Whatever's distracting them from stealing, they'll usually keep their hands busy being a help rather than a burden.
Other times, the trio and the twerps will get mixed together, separated, and lost. When this happens, It happens more often than one might expect, but a good example would be Episode 155, "Forest Grumps;" while everybody is running away from some angry Ursaring, Jessie ended up with the Twerps and Misty ended up with Team Rocket, The members of Team Rocket called a truce until they could regroup, but they went right back to stealing once everyone was back together. This trend isn't so much about them being good as it is about them not being evil, at least temporarily.
They've also made efforts to stop other evil teams from the different regions. They've thrown themselves directly in the way of Team Magma, Team Aqua, Team Galactic, Team Plasma, and Team Flare's schemes. Of course, this is mostly so that Team Rocket can conduct operations in those regions without having to contend with these rival gangs; apparently, Team Rainbow Rocket is not the goal it was in the games. Regardless, Team Rocket's willingness to help clear out those regions is certainly appreciable.
Looker, an investigator for the International Police, will vouch for Team Rocket's assistance in stopping evil teams. They formed an unlikely alliance with him to stop both Team Galactic and Team Plasma. As far as Looker is concerned, Team Rocket is alright.
The Team Rocket trio has even been known to thwart their own organization's plans. This is especially true when Cassidy and Butch are the masterminds of a particular scheme; They'll often try to steal their stolen Pokémon and even battled over them (Episode 222, "A Promise is a Promise"}. They also infamously sabotaged one of Matori's plans when they realized they were deliberately left out of it (Journeys Episode 24, "A Little Rocket R & R!"). This just adds to the wonder as to how they've kept their jobs for as long as they have.
Team Rocket has even been known to help save the world when the situation calls for it. They've helped Ash and co. to stop the Legendary birds (The Power of One), a machiavellian Malamar (XY Episodes 19 and 54), and a giant Claydol (Advanced Generation Episode 104, "Claydol Big and Tall) among other world-destroying threats. By their logic, if anything happens to the world, they won't be able to steal Pokémon anymore. However, that doesn't change the fact that they were the heroes in these scenarios.
Speaking of being heroes, the trio actually got the chance to become real heroes in Pokémon Chronicles Episode 7, "We're No Angels!" They ended up in a farming village where they were mistaken for superheroes and tasked with saving the day. They found the good guy business suited them and even considered staying. However, they soon forget their heroism and return their attention to chasing the twerps and Pikachu. This episode proved that while they could become heroes, their hearts lay in villainy.
With that said, there are still plenty of ways that Team Rocket is inadvertently helpful. This includes episodes where their sole intent is to steal Pokémon. In fact, their helpfulness in these scenarios counts on their interference.
Team Rocket tends to introduce a necessary conflict to a given scenario. If a Ditto is having trouble learning to use Transform properly, Team Rocket will coerce it into doing so (Episode 37, "Ditto's Mysterious Mansion"). If a character of the day is about to lose a battle, their interference could lead to a rescheduling of the match and give them time to rework their strategy(Episode 166, "Two Hits and a Miss").
If a Trainer needs a Pokémon to trust them, all they have to do is save that Pokémon from Team Rocket (Episode 84, "The Lost Lapras"). Similarly, if two Trainers are having a disagreement, they can reconcile their differences by battling Team Rocket together (Advanced Generation Episode 118, "Less Is Morrison"). In solving whatever conflict Team Rocket introduces, one can attain clarity and find a solution to a more personal problem.
There are also all the times that Team Rocket helped Pokémon besides their own evolve while trying to steal them. Often, they'll back a Pokémon into a corner with one of their mechas or their own Pokémon, which will cause the opposing Pokémon to evolve so it can fight back.
Thus, these heinous criminals have been directly responsible for no less than 26 evolutions throughout the anime's run; many of these evolutions were from Pokémon belonging to Ash and his friends. In this regard, without Team Rocket's attempted thievery, Ash may have lost a number of key battles that required his newly-evolved Pokémon to win.
In this same vein, Team Rocket might also be inadvertently helping Ash with his training. By constantly going up against the twerp, they provide his Pokémon with the necessary experience points to gain levels and evolve; they're essentially helping Ash grind before any of his major challenges. On days when Ash doesn't really have to battle anybody, he can count on Team Rocket to keep him sharp.
The world of Pokémon would be a much darker place without Team Rocket there to brighten it up. Between their unintentional assistance and their genuine acts of heroism, they've helped people and Pokémon far more than they've hurt them. They may not like to admit it, but they can be pretty good guys where it counts.