I think that Freebitco.in is more a faucet than a real gambling site although lately they have been adding betting to their platform.
It was a faucet-only site years ago, that is true. I don't know exactly when they had added betting to their portfolio, it has definitly been around for some time now. They eg. hosted a bunch of Game of Thrones related bets during the final season last year. They hosted uncommon bets like "Oscar - Best actor" or "Will britain brexit in 2019", too. Definitly worth to watch if one prefers such bets. I hope major casinos and sport books will add a small section in their page to esports in the near future.
It is "balance demand and supply"-thing. The more people want to bet on esport games the faster sites will add them to their portfolio. Btw. sportsbet.io offers a lot of esports-related bets (League of Legends, Dota2, CS:GO, ...). They are definitly one of the major (crypto-)(sports-)betting sites out there 