Foreign tax credits often reduce US tax liability.
Taxes may be reduced but not eliminated.
And....There are the fines for not filing, and the irritation and time needed to file, if they do pay taxes. Finally, many foreign banks will not accept American citizens as clients because these banks don’t want the hassle of dealing with the American IRS.
Against my better judgement, I will feed the troll. If you don’t file, there are automatic penalties that no foreign tax credit can offset.