A PHD is great and would maybe earn you 200k or less in the US. Boxing earns them millions. To say they box for the hell of it probably isn't accurate. It would be really hard to say anyone at the professional level did it solely for the sport. Its always about money, ego, pride, family etc...
John Ruiz. He doesn't even follow boxing at all... He was on some blog talk radio show one time and somone i think Paddy asked Ruiz about David Haye, and Ruiz said he doesn't even know who David Haye is LOl
to be honest this is the big con of modern civilisation for me... how can you say someone is too clever to be a boxer when being a fighter and not having to overcome that 'fear' from bullying and such shapes who you are as a person more than anything else (in my opinion) when you're young. being a doctor gives you spiritual satisafaction and i'm not taking away from that, but i'll ALWAYS maintain that people who can't stand up for themselves when they are young and throw themselves into study without confronting their fears will always have less character than someone with half a brain but who had the self respect to overcome that. why should making money be a reason not to pursue something that equally (at the end of the day) shapes you as a person - but in a totally different way?
i fought amateurs and was successful but there was something else i wanted to do and i stuck to it. mind you, i never really considered going pro because i wanted to do this so badly...