I can entirely understand how they feel, to be honest. They are all self-made people and therefore have a strong work ethic. Leaving an obscene amount of money to their children could be disastrous: what would the children do? They certainly wouldn't bother working and they'd have more money than they'd know what to do with.
So, what? Become one of the idle rich, partying all day and night, out of it on drugs and alcohol because, well, they can afford it, can't they? And they certainly don't need to save the money for anything serious or important, already got that.
That is the fear, I believe, that these celebrity parents have and I'm sure they've seen this descent into chaos and, ultimately, poverty that children of the very rich have suffered.
Of course we talk about leaving our children everything we have. But everything my DH and I might wind up with would probably do little more than pay their gas and electricity bills for a few years.