It's a contact sport. Takes talent, and strategy. It brings family friends together to watch. Gives us something to watch while waiting for food on Thanksgiving! :-) For the people playing it... they make good money, play a game for living, and get to be on TV.
I do not particularly enjoy playing it myself but people that are my age like the part where you can pretty much go full speed hitting someone without getting in trouble. People in my mind like to watch it because they enjoy fantasy football and want to see how their players do which makes it a million times more exciting.