If you really want to dig into it, the problem is that there are a huge number of students who don't know anything at all about how or why to learn. If they actually wanted to learn and understood how exercises help them, the fact that they're all well-known problems really wouldn't be a big deal.

But universities are businesses now. They produce diplomas in exchange for money, and interrupting that with details like "this student shouldn't be here" costs them money they can't afford to lose.