Well in my opinion, I think that personal stakes in something are necessary for a hero to get invested, but not for them to get involved. If the villains present enough of a threat to order and the wellbeing of others, then heroes will step up. I don't know if this has already been said, but, villains don't have to threaten the heroes directly to be interesting, in my opinion. It adds risk, yes, but for me, some of the best villains were the ones that galvanized the heroes into action.