[_yosefk]

That might make sense, but why the difference between Europe and the US, if in fact it exists as the grandparent claimed?

It's true that it's costly and hard to test one's skills. The trouble with grades though is some people cheat brilliantly on their tests and others, some of them really good, test badly (if they're bored they don't prep, screw the grade average, etc) and some of the latter are actually extremely pragmatic on the job. I don't quite understand it but it's there.