For every fledgling sport that is on TV (ESPN or otherwise) there are plenty of others that are not. Horseshoes, Bocce, Darts, Ultimate Frisbee and many others, like Disc Golf, have very serious players, but no TV coverage.
Some sports only get coverage because of the Olympics. Would Curling ever make it to tv screens if it wasn't an Olympic sport? Doubtful.
But even that isn't enough. Show Jumping is my wife's specialty, it's an Olympic event, yet barely gets covered even in today's 24/7 super cable overload coverage.
Basically to get a sport on TV, there needs to be significant investment (monetary and time) as well as a dedicated person or group that is wholly dedicated to creating a product that will be entertaining to watch.
The UFC nearly folded before Zuffa took over and created a marketable product. Now it has taken off. In Disc Golf, Derek Hastings can't even pull together enough investment to see his documentary through to completion. We're lacking money and visionaries, disc golf on ESPN is a very long ways away.