One big reason is that the fans watching can easily project themselves into the game and feel as if they are actually on the field playing. They can see where the play should move and the pass be made. Even watching the small screen at home the instinct to kick the ball presents itself. Watch fans feet sometimes as they are drawn right into the action just as spectators. It becomes a compulsion. No time outs. No commercials to break momentum. Two hours and you are on the road. Oh, BTW no kneeling in protest before the games either.
I am always amused that I played lots of basketball but never enjoyed watching it and nerver played soccer but do enjoy watching. But that’s me.
What was the movie with Peter Sellers... “I like to watch”.