There actually is an estate tax after death:

https://www.irs.gov/businesses/small-businesses-self-employed/estate-tax

Right now it only kicks in after 15 million. A decade ago it was still 5 million. But it doubles to 30 million for a couple.

For the really wealthy people, they need to pay to obfuscate the rest of the money thru trusts and offshore banking, which they'd rather not to pay to do.

Which is why they're still pushing to raise the cap every year.