A tax on simply exiting the country is a very foreign concept to Americans I would assume.
Looks like the limit last year was $120k. Only 17% of Americans make more than $100k/year. Only ~5million Americans living abroad, or 1.5% of the population.
I'm sure those numbers are correlated, but I'll bet its under a few hundred thousand of people who are burdened with the tax. Even then, the benefits also are pretty nice.
Try owning a stake in a foreign company (CFC) though, that's a nightmare with often unavoidable significant taxes.
Also more and more non-US banks won't take US citizens as customers because they don't want to deal with the US's FATCA requirements.
No other developed country has these sorts of requirements for non-resident citizens.