Maybe he has tax problems. Most fighters really do miss their glory days and are constantly trying to get that feeling back. Maybe he just loves fighting. Probably a combination of everything above.
Now we know why retired Marciano was carrying with him all these concealed banknotes, lol. Anyone remembers smug Roy dancing his way to the ring to the tune of "Mr Invincible"? When you're that kocky and juiced to your eyeballs, reality is bound to catch up with you sooner or later. I suspect Roy has yet to realise what's really going on.