His motive (money, love, adulation etc) is irrelevant ...he's 53, looks washed, doesn't put up good matches, is wincing in pain after chokeslams, is reportedly in pain and may need surgery....if that isn't hanging on too long I don't know what is....
To make it clear, he's obviously hung around too long....clearly YEARS past his prime. Any person can see that. BUT my point is, it's not really an issue when he only fights ONCE a year or so. It's not like he's doing a Ric Flair, where he retires and comes back b/c he needs money.
He's an attraction if for nothing else than just his entrance being a spectacle.
Undertaker and Wrestlemania are synonymous. And given his character, he can't really be an on-screen talent in any other form other than fighting.