[incompatible]

I was interested in certain sports as a teenager, but grew out of it. I can think of a couple of reasons. Firstly I moved around a bit, to different cities and countries, and parochialism seems very silly. If you don't care which team wins, a lot of interest in sport disappears. Secondly the sports themselves are extremely repetitive. Once you've learned the rules and seen a few games, there's not much more to learn, it's just variations on a theme.

Edit: I'm referring to spectating, not active participation. I'm sure there's a lot more to learn, understand and enjoy if you actually play.