Because they bust their ass doing what they love.
It's sad to see Edge go, another original WWE supserstar is leaving and with that WWE continues to slowly die... or rather, become irelevant.
It's for his own health and like he said, he should be thankful that he's not in a wheelchair now. I'm happy he isn't taking any risks, safety first.
Thank you Edge for the wonderful moments, the happy times, the bad times, the vampire attitude with the Brood, the sillyness of E&C (Edge and Christian), the epicness of E&C, the table matches, the later matches, the TLC matches, the shocking moments, the live sex celebration with Lita, the cashing in the money in the bank on the Undertaker, the epic return to the Royal Rumble and the final last match at Wrestlemania this year. You're leaving as a champion...