Being truly principled is difficult for most people for two reasons:
(1) Being principled requires sacrifice. It means going without, which for someone who's used to pirating lots of games/movies, is the emotional equivalent of cutting off their blood supply. Seems like a very trivial and firstworldproblem issue but it's just an example of a low-cost sacrifice a lot of people can have a tough time dealing with.
(2) Being principled can be dangerous. Stepping in to help someone being beaten up is damn dangerous, and even a principled person has to decide if it's actually going to help, or just end up with two people bashed up instead of one. Or like that one Mexican politician who wasn't corrupt and genuinely tried to face the Mexican drug gangs, who survived two assassination attempts (one of them costing her husband's life) before finally being killed recently. She was principled, and she died for it. Most people won't have to face that level of dedication but they might have to deal with still dangerous issues where it might take someone principled to do the "right thing".
So basically, most people (including myself, make no mistake) like the idea of principles, but only if they don't have any major negative sides to them. Otherwise, they'll decide that they only have one life and it's not worth ruining or sacrificing for no perceptible gain.