Numbers can be interpreted so many ways- such as a poster pointed out about why there are so many from two very populous states. Regarding Wisconsin- the distances involve either going up and around Lake Michigan or down and around greater Chicago (or I suppose an equally time consuming route using a ferry)- neither is that easy/fun. People in Wisconsin tend to ignore the U of Michigan in general- seeing no great advantages academically and often a nicer campus in Madison. A biased view, but that lake is a huge barrier to frequenting lower Michigan.
Michigan seems to have lost its mission as a school to educate it’s students. Perhaps having Michigan State makes it less important as a mission. I have also heard there is the money issue- getting more from OOS students helps the budget. Different states treat their flagship U differently.
Going home weekends depends on the campus atmosphere. Some campuses make a student want to stay to not miss the weekend activities (and not merely sports) while others lack that culture.