It depends on the school, the deans, the professors, the reputation, and the tradition.
You can find schools that don't cut any slack or at least don't make life easy for a student. You usually know that before you even attend it.
I have seen classes that have averages which are low compared to other classes but it has to be taken in by context and the course. The subject matter could be a lot more conceptually complex or the mathematics was extremely detailed and required a full range of knowledge. In those cases I can see why they curve simply because the material takes years to master. There are certain times when they get a chemistry major to pass quantum physics with at least a C so he can actually get to his upper division classes and start learning what he needs to learn.
It is all relative.
"I've learned . . . that life is like a roll of toilet paper. The closer it gets to the end, the faster it goes." ~Andy Rooney
"At last I shall have time to devote myself seriously and freely to the destruction of all my former opinions." ~Descartes
“The first principle is that you must not fool yourself—and you are the easiest person to fool.” ~Richard Feynman