Bags - I agree completely, and a motivated student can get a fabulous education at almost any school in the country, but ...
The environment does make a huge difference for most students and the seriousness of fellow students is a huge part of that environment. The difference between walking out of a class and continuing a discussion of some interesting topic with classmates vs. discussing the keg party on Friday is real. And even if most of the time is spent with fellow athletes, that still makes a difference - a much higher portion of those athletes at Stanford are actually attending serious classes and doing serious academic work than those at Kentucky or Florida State, and it does make a difference in the level of temptation to slack off if you are not a athlete particularly driven to succeed academically. Uconn WCBB has academic competitions within the team every semester which I suspect is not a standard practice at all schools, and I am pretty sure is not a standard within all of the Uconn athletic programs either. But an academically inclined athlete will feel they are more in tune with the whole student population at a school with top flight academics and it will be easier for them to feel part of that whole community.
It isn't that you cannot find a group of similarly serious students as 'State U' it is that you are more of a minority there than at 'Super Academic U'.
By the way - it is the same in HS as well - I went to EO Smith in Storrs and 50+% of the student population was from a family connected to Uconn, and so I was surrounded by high achieving students and felt part of a large segment, perhaps the majority, that took grades and homework very seriously. That was unique amongst my freshman dorm when I got to college - everyone else had been seen as a fringe part of their high school classes because they took the school work seriously. And when I transferred from an Ivy to a non-ivy half way through school, there was a noticeable difference in the seriousness of students, I found my set, but it was a much smaller universe of the college population.