I tried to verify it, and based on my verification, there are only a few sportsbooks that have horse racing.
Yaps, cause the sector are not quite popular.
Like, could be these sport only famous or quite interested in (UK) or some country (and pardon, usually a rich sport). Meanwhile, a sport like (Basketball, Football, e-sport) are quite high because all people from different age enjoying and can access more often to see these sport.
More markets to be open, more money casinos need to spend for the operational. If the sport sector not give a good money to the casino, usually they just wasting money (that's why we rare to see this kind of sport). Unless casino like stake or other casino who have a good revenue.
BTW anyone facing some problems today? it's keep loading trying to join the free poker roll. I missed the match.

Trying to restrast my wifi and other still loading