And the disincentive effects are much smaller than taxing the equivalent in directly earned income.
When my parents die, assuming they go before me, I don't see why the government should be involved. To be clear, my parents are well below estate tax thresholds, but the underlying premise is the same. Someone's relative dying and leaving them an estate shouldn't by a taxable event as far as um concerned.
$66B should be a lot of money, but our federal government doesn't know what it means to balance a budget. We could easily cut $66B in current spending if we cared.