It's hard for me to say "no" (to a Rolling Stones tour) because I've been a fan for so long, but I can understand the reasoning behind Mick not wanting to tour.
He's the one who has to work the hardest on stage--and let's face it, the guy isn't getting any younger. All Keith and Ron have to do is stand on stage with cigarettes hanging out of their mouth and look half (or just plain) dead. Bill is invisible and Charlie looks like Grandpa (from the Munsters).
Mick's the one that has to run up and down the stage like a maniac night after night and prove he's still got his sex appeal.