They missed something in this article. There is actually only 1 indoor velodrome in the US. The rest are outdoor.

What's important about that, is, given any locale's elite cycling community, there's little reason to race on the track during summer when it's nice enough outside to square off against national level competition on the road on any given weekend if you're willing to drive a few hours.

Move to the winter, and Cyclocross takes the rest of the would be indoor track racers. Track is great, and a ton of fun, but it is largely out of reach for most of us that compete because of lack of well, tracks.

Another thing - no one starts racing at the paid professional level. Without amateur/junior racing, those people can't move up, because they can't start. This is a big factor in why the sport's declined so much... No more amateurs.