it stems from our archaic past, when we were all a part of a tribe or a little community, competing for resources and land. I think the NFL does a good job tapping into this collective subconscious and directing this behavior towards a particular team (whose performance, let's face it, has no real effect on your life) and profiting from it. NFL stars are like the tribal alpha leaders of the past that everyone looks up to and strives to be like. This is our innate nature as males to observe the alpha and mimic his behavior. Its a great market for army recruiters too, thats why u see the close relationship the army got with the NFL.
"Tell our people to tool up" -Marlo
"Tell our people to tool up" -Marlo