With the major sports: baseball, football & basketball, once your skills deteriorate, either you retire or get cut.
With wrestling, guys with name value can manage to eke out a living on the Indy circuit or in Hulk's case, just being Hulk. This is what keeps these guys hanging around when they should've moved on to something else a long time ago.
I heard Ricky Morton on Austin's Podcast, recently. The guy is pushing 60 and still wrestling in small shows.