It is kind of a weird custom we have here in the USA, we scratch our heads in amazement when the rest of the world goes gaga over the inferior type of football, but the rest of the world returns the favor when we go gaga here.
Oh sure there are artistic/politically correct/sensitive wienies that look down their nose at the game, but they don't get invited to the parties, so screw them. Having friends and kids friends come over, eat a little to much, drink a touch too much, and shout at poorly thought out strategies is great fun.
Mostly is is a counterpoint to our Thanksgiving tradition. On thanksgiving, we are going into the winter and we celebrate the bounty of the land with our family. Super bowl is the time where we close out the doldrums of the winter and hang with our friends.
To be honest, the food is better at super bowl parties. Thanksgiving is steeped in its own traditions, but by being hidebound you are limited in what you serve at the party. Super bowl is straight free form. Gotta have some Mexican, this year in honor of New Orleans we are doing mufflata sandwiches (it is the olive spread that makes them great). Beer and chips, buffalo chicken legs, soda for the boys (you know how hard it is to find stuff without that high fructose corn syrup crap!). In other words, top quality junk food.
I can't remember when I first heard this saying, but it is so true;
"Football shows what America does best...committee meetings followed by violence."