Guys who do it simply for money don't put in the work he did to get where he was, and then try to get back from a bad injury. This guy was an undersized R4 pick who became an elite EDGE eraser by working on his technique until it was great.
I agree that for him it's about identity, and pride. He knows he's good at playing football and loves the game. He wants to do what he's really good at. Nothing wrong with that.

He has certainly made enough money, and if he has to limp away from the game he's got that. I'd bet he'd trade a good chunk of that money for never having the injury though.