My wife used the intersession courses every opportunity. Her courses werent 'jokes" for what its worth. She usually took something slightly harder that she could focus completely on. I treated summer school at State the same way.
but they do get a lot of students using intersession and I have never understood why MSU doesnt employ it
I think we have one intersession in May. Been a while, but when they were originally rolling it out, professors pushed against it. I believe their argument was that they didn't believe the intersession courses would maintain their academic rigor. Which makes sense to me; I don't think the time is too short to get a full class in if the student is focusing on it. Summer school is 19 days of classroom time, an hour and fifty minutes at a time. Intercession is 15 days, 2 and a half hours at a time. So a significant drop in days (20%) but extending the class room time by 40 minutes each day. I just think the vast majority of students study so little that they aren't really prepared to cover a topic rigorously in that short a period of time or to concentrate for 2.5 hours straight and then come back and study in the afternoon. So I assume that the path of least resistance is to cut back on rigor.
That said, that same argument is probably stronger when you are talking about doing two courses in summer school as opposed to one in intersession (which I think is limited to just one class?), and the few summer school classes I took didn't seem lacking, but it's hard to say since I obviously didn't take those classes during the semester. Maybe they were and they just felt similarly hard because of the way they were crammed in.
But regardless, my friends that took intersession classes at UM did take joke classes and they were essentially using their parents' money to buy them extra time during the semester. But maybe the same classes were jokes during the semester too and there were other classes that were more rigorous that they avoided because they weren't jokes.