The limits for the estate tax in the US are pretty high. It's over $20 million if you are married. That means those who are hard working and frugal will most likely never pay an estate tax. Hard work and frugality will allow you to slowly accumulate several million dollars over your life.

At the wealth levels at which the estate tax applies, a fair amount of luck has to factor in. Having been in the right place at the right time. That has little to do with morality because many other people had the same behaviors but never got lucky. The estate tax is more a tax on luck than it is on hard work and frugality.