Firstly, students enter at a time when they're still figuring out what life is. You could do a lot of research on how to maximize the best professors or network in a field but most won't predict what specialty they'll end up with. Even if they do, they're so young they could not know how to judge the quality of an authority yet, so who is to say you will estimate that correctly?

The other reason people want top schools is for networking with other students. Some people will get a lot out of that and others won't. There's a bit of randomness involved. You could maximize your odds of being surrounded with good networks by going to the best school but honestly, I doubt you can truly predict the worth of that for an individual student.