Actually, reputation matters. If a college were to give out uniformly high grades then they would pretty soon not be trusted. And organizations that do "ranking" would be pretty savvy about such things.
It would also be pretty hard for a university to manage such a thing, since grades are given by individual professors with individual preferences to individual students with individual skills.
Some places, however, attract very able students. So, a 3.4/4 earned at one place might be better than a 3.6 earned elsewhere where there is a lower standard.
If the firm "cut-off" really happens, I assume that it is pretty low and that other factors might provide exceptions. Such a cut-off might not be disqualifying, but only result in a "sorting" of applications so that the more promising ones can be handled first.
Employers, on the other hand, are looking for skills, not grades. But they, too, want to spend the effort in hiring on promising candidates. Grades are only a part of that.