I think another factor why pro rivalries are losing their luster is that fans themselves move and live in many different places now. You add to your identity and can associate yourself with other teams.

Also it seems every handful of years a league is realigning. As a Reds fan growing up, the team I was raised to hate was the Dodgers. I still dislike them but it doesn't matter now that they are not in the same division.

College sports maintain because no matter what else I do in my life I will always be an Ohio State Grad and I will always get hyped for The Game.