I've always felt that this is a misconception. My friends did a ton of drugs, had parties and participated in hobbies, especially in college. Now they're all Engineers, PhDs, Doctor's and Entrepreneurs. They just happened to work hard at school too. They don't have kids cause they're busy, so it might be as bad.
But no, it's because they're rowdy kids doing 'bad things'.
You just suggested that a lot of ivy-league schools are second tier. I'm not sure you're very representative of the vast majority of people.
In Texas, there's stuff like Stanford and Cornell, which is ivy league -- 1-2 kids might do that. Then we have 2 top tier state schools, then it's the other stuff.
Everyone else I work with got some degree from an Ivy League. Half have PhDs. It carries some weight and I think we get better VC funding and it's easier to get customers, but I don't think the degrees do much beyond that.
But no, it's because they're rowdy kids doing 'bad things'.