But still the sector who are betting in here small compared to other sports books like (E-sport, Sport like Basketball or Soccer, etc). That's why we rare to see some casino to have sportsbook sector with (Horse or animal racing). Unless you have big revenue like stake, they can wasting on somethings sector are not quite big enough for just make the casino it's provided some sector gambling we can't see on other casino (even not gonna to bring a huge revenue).
I tried to verify it, and based on my verification, there are only a few sportsbooks that have horse racing.