It is a philosophical point. Beer is still served in the Flatirons Club and at Coors Events Center. It is served at basketball and volleyball games, which constitute something like 50 events, compared to six for football. But there is big money in the boxes and the Flatirons Club. At least they get free soft drinks.
Concessions are a large money-maker.
Alums are the ones who really want beer in the stadium. There was a satisfaction survey, in which most people apparently reported being happy with the ban, although the numbers seemed a bit high. The fee has created immense discontent over the years. In particular, one might call it an abomination that graduate students are forced to pay it. The vast majority of students are forced to pay the fee, whether they attend athletic events or not.