This is a recent phenomenon. In Edsall's 1st tenure, the student section was pretty full, basically until game results were no longer in doubt. By the end of former "Coach" Pasqualoni's final full season, the PA announcer had to stop the already joke of a refrain of "The Best Student Section in the Country," as he was only referring to aluminum benches.
Cost/Benefit
A significant issue is, as always, price paid for entertainment value received. Game tickets and transportation can cost -0- but how about time? What if a student cannot get a seat on the final bus? The tailgate is entertaining and worth it. The game is not. It's that simple. Semantics or not, on-campus facility wouldn't change that and it's going to take more than two games to get it back, particularly with the University about embark on the Independence path.
Instant Gratification
It's been growing since the dawn of cable TV really. Not entertained by what you're watching? You don't even have to get up off the couch to turn the dial. Just a few click on the Silent Shifter of Wonder to see if something else can hold your attention.
Cost of being a Student
I went to UConn as an out of state student. Disregard the notion that my scores may have not been high enough to get in now (I.e the educational is set higher), I paid somewhere in the neighborhood of $17k ('96) as freshman and $24K as a senior ('99). In-state estimates now eclipse $30 grand (OoS > $50k). If a student can't afford tuition in the first place, they certainly can't afford to flunk out.