After you have so much money you must try to think of frivolous things to spend it on. It becomes difficult to waste enough money to keep it from simply piling up.
On a smaller scale, you may like steak but you can only eat so much. You may like nice cars but you can only drive one at a time.
There was a great line from "Wall Street" (I think) where some money-hungry big shot was asked how many yachts could he water-ski behind.