They might also organize private gatherings and parties on this vessel. Before boarding the yacht with your closest pals, stock up on meals, iced beverages, and cocktails.
Privacy immediately comes to mind. They have a hard time getting it, and the yacht gives them a lot more privacy than they may have on land.
A superyacht is mostly or solely used for leisure, and it is large enough to accommodate large family gatherings in complete secrecy away from prying eyes. This appears to be the wish of a billionaire coming true.