Ask HN: Why Are There `Remote: Only US` or `Remote: Only Europe` Jobs?

I am under an impression that there are limited software engineers in US and EU, which is why they have to hire from everywhere else. And with anti-immigration regimes companies are now turning towards remote work. But seeing job listing with `Remote: Only US` or `Remote: Only EU` makes me wonder if I am wrong in thinking that?

Can someone here who is responsible for creating such vacancies or anyone who knows clarify about why they have this condition?