All of these. And I would add shame, low self esteem and getting you've got a point to prove and not letting someone else get the better of you into the mix (not all of them at the same time, though!).
I have no stats to back this up, but I'm pretty sure there would be gaps in those grounds for certain games, under certain conditions.
I don't really care either way - people can do what they like. But what did make me laugh was the people involved in the mass exodus at 40-ish minutes who...
A lot of boxers aren't really known for their intelligence. Probably something to do with the amount of times they've been twatted around the head.
I'm guessing a mixture of ego, appetite from the public and the lure of a load of cold hard cash will 'force' AJ will fight on.