[DaFace]

To me, it's a combination of a ton of things, including:

1. Changing preferences (half of my friends give zero ****s about sports, and I'm in my 30's; younger kids seem to have even less interest)
2. A constant stream of decisions that have been made in the past ~15 years that have slowed the game down, increased the role that subjective officiating plays, and reduced the amount of athleticism in the game through far fewer practices and rules that have removed big hits (though I don't disagree with that one philosophically, you have to admit that "jacked up" was more fun)
3. The sports media, like all media, trying to make "news" out of every little controversy rather than just focusing on the game.