Originally it was just a really high tax rate at the highest bracket. This accounted for a monetary system that is essentially gamed. In the US the government reversed this under the theory of trickle down economics. This allowed a large group of people to greatly grow their investments and their wealth accordingly.

Inheritance tax is used to recoup some of these lost taxes but it is a poor way to do it. The correction should be at the beginning not the end. I agree with you.