besides spend it on frivolous shit like yachts and planes and stuff, there's no way it's all liquid. do they just park all their billions in a bunch of investment vehicles and wait for it to propagate itself? don't they get bored of just waiting and watching line go up?
But hoarding as much wealth as possible serves to keep the value of wealth high and protects them from being usurped. A big, fat dragon stays big and fat by eating little dragons before they're able to attack.