It makes sense during a tactical fight that the good guys who are more skilled and have more power would be able to take out mooks and the like who are likely inexperienced due to just being mooks. Only the big bads are likely to get a kill and by then the heroes likely have something to win with.

Remember, if it's a fist fight bring a knife, if it's a knife fight bring a gun, if it's a gun fight don't go. It's not bad for heroes to think like this.