A LOT of people (70,000) go to PAX in Seattle each year and they have one of the League of Legends tournaments there and it takes up a whole floor and a lot of the people who go only go for that. There is money, just with Twitch I don't think there is money in broadcast television. Plus StarCraft is just not a thing here in the states.. In Korea it's huge, to where they still put StarCraft characters on Pepsi, Doritos, etc.
I would guess the thing with ESPN is the people who watch it are sports fans, and sports fans are not necessarily esports fans. It is just as popular with kids today to watch others playing games like Minecraft as it is to actually play it. Watching other people play video games is becoming big, I just don't know if the market is already saturated for cashing in on it.
However, if you look at the history of X-games type sports.. when they first came on television it was a joke. Nobody saw skateboarding, BMX freestyle, or snowboarding as a sport, they were hobbies that mostly went along with smoking pot, and kids who sit around and smoke pot aren't athletes, right?. Well, now they are huge and easy to find on television. Right now the gamers out there know where to watch this stuff for free, but if it crosses over to mainstream then television is still the most popular medium and there is money there. It's a question of whether eSports will cross over to mainstream.