After so many tours, so many shows, even when the touring has become extremely well planned, a lot easier and a lot more luxurious, it becomes routine. Been there, done that, kind of thing. And it gets boring. For people like Mark, creating is key, and touring therefore becomes a duty. In and out of planes and hotels, soundchecks, the static setlists, etc. It's a job. For sure it beats working at McDonald's, but when you're successful and wealthy and can actually choose to do whatever you want, why would you do boring work? Plus the man is turning 70 and has nothing more to prove, and he honestly doesn't owe anything to the fans either.
I applaud Mark's honesty, and I think we can expect some cool projects down the line now that he can free up resources by not having to tour as extensively. One era ends, and another begins.