are possibly trying to relive their youth and continue to play.. but.. I think its another reason: Most musicians don't have anything else to fall back on, job-wise, so they HAVE to keep playing to keep paying the bills.. I know quite a few musicians who were TOP NOTCH in the 80's.. should have made it huge, but didn't, for whatever reason - like me lol.. And now they all play in multiple bands, playing every night.. I think its because they're too old to get regular jobs, or too lazy to get regular jobs..
Friendship is like peeing your pants.. Everybody can see it, but only you can feel the warmth..