A mansion with everything you could ever want is "only" tens of millions of dollars, so any billionaire has as many as they could want. But you you want to go to different cities for different events, and settling in to a new place is such a hassle. You ever spend a week on vacation or at a relative's house and, for the first few days, every time you wake up in the middle of the night to take a piss, you have to remember where you are and where the bathroom is?

What if you were so rich that this is the biggest remaining problem in your life? Wouldn't it be nice if you just had one mansion set up the way you like, and could take it with you?

(Nobody should have this much fucking money.)