Well, in our society we have things that you might use your intelligence on, like politics, but people really can't get involved in them in a very serious way -- so what they do is put their minds to other things, such as sports. You're trained to be obedient; you don't have an interesting job; there's no work around for you that's creative; in the cultural environment you're a passive observer of usually pretty tawdry stuff...So what's left?
...And I suppose that's also one of the basic functions it serves society in general: it occupies the populations, and it keeps them from trying to get involved with things that really matter. In fact, I presume that's part of the reason why spectator sports are supported to the degree they are by the dominant institutions.