>As I understand it many first-world governments confiscate some portion of estates.

Of course.
If you listen to the arguments in favor of it, they all seem to hinge on a "social justice" justification.
From an economic standpoint, they are probably a drag on economic growth.

The taxes themselves contribute very little income to our government - something like 3/10 of 1% of the federal government revenues come from estate taxes.

In spite of the tiny revenue for the government, the estate planning to avoid estate taxes make a very nice living for some lawyers and accountants.
Of course that means that many small business owners and farmers are making decisions based on estate planning and not maximizing business value, so the total economy shrinks an invisible little bit, meaning less jobs and opportunities for people who need jobs and opportunities.

The sound bites suit some politicians, and resonate with certain voters.
Many of those same voters who like the idea of taxing away other people's estates.. do in fact do estate planning themselves to minimize their taxes.
So, it seems that taxing estates away from the families is ok, as long as it is somebody else's family.
Hmmm.