As far as I know, the countries that still use cups are the USA and partly UK.

And even then the second you get into anything related to science or medicine in the US things go to metric. That said, it's not 'that' hard to just get used to converting it on the fly in your head. At least for liquids. Not always practial in how it works out. But being something like 0.1% off on something is seldom much of a big deal with cooking.

The weirdness of using volume instead of weight for irregularly sized ingredients is a whole other thing though.

All that said, I agree that it'd be nice if everyone just used metric. But I think trying to enforce it would hurt more people than it helps.