To thine own self be True Neutral

[JennTora]

I remember in the cartoon Jackie Chan Adventures there was the idea that if you eliminate a villain it leaves a literal power vacuum that can be filled by a stronger one. The idea makes perfect sense if evil is an eternal force. So maybe sometimes True Neutral just feel it's better to stick with the villains they know how to beat, I think Mordenkainen had a similar view, right?

Plus you don't want your good guys getting lazy while the bad guys are prepping for action.

Besides, with no true villains to fight, all the lawful stupid paladins would go around harassing people for inane things. Oh... wait...