Everyone has their pick as to who they deem the definitive Batman actor, but for many that title belongs to Kevin Conroy. Having voiced the Dark Knight in Batman: The Animated Series, the Arkham series of games and other animated features, Conroy has been playing Batman for nearly 30 years, so his connection to the character runs deep. Perhaps that's why he feels he has a special insight into the mind of the Caped Crusader.
Speaking about his favorite character with as reported by Den of Geek, Conroy shared his thoughts as to why Batman never kills.
"That was something they established early on and it ended up benefiting them so enormously because years later they realized, 'Wait a minute, we have this rogues gallery of crazy villains and they're all in Arkham Asylum," Conroy said of the initial decision for Batman to leave his nemeses alive and (generally) intact. "Let's get em! Let's get them out of there and let's open it up.' And then you had the whole Arkham series of games that they were able to do out of that."
Of course, that's what happened because Batman doesn't kill. As for why he lets his foes live, the answer is perhaps less character-driven than you'd expect. "If he'd killed any of those people, they wouldn't have been available, you know what I mean? I love the fact that he doesn't kill."