It is hard to become EXTREMELY rich honestly. You may have inhereted your booty but back there, somewhere is probably a robber baron of some sort.Or just as likely got that way from working hard or learning special skills that pay well or making risky investments, or playing professional sports (like basketball) - not every rich person is a crook or likely not even the majority.
To reduce their tax load.
Note, that I did no say "wealthy" because you can indeed get that way through hard work and being clever.