Most yacht owners don't live on them full time. (they may have a paid crew that does) they take them for vacations. They are not really transportation even though they often will go to multiple close destinations.
I'm also confused about people who own many vacation houses. Why not just rent a different fancy house each time? Less expensive, less trouble, more variety, you can experience more places...
Staying in your own yacht means that you have all the things arranged like you like it. You can't repaint your hotel room. You can't control how firm the bed is in your hotel room. Most hotels give you a choice of pillows - but you have to do something with the ones you don't like without taking them out of your room. Your yacht/house is never booked when you want to go - which can be a big deal.
There is no reason someone with a yacht can't stay in a hotel. I suspect many with a yacht spend more nights in a hotel than all their houses/yachts combined.