I think you would get many users with horse racing, with sports betting you have 100's of sites and much competition in the bitcoin world.
There are very few bitcoin with horse racing, and the few there are, are all flimpers.
I know you said in earlier post more difficult to set up horses, but sometimes a more difficult task renders greater success.
I know hey laying of horses and greyhounds was also very popular a while ago. Now probably still.
That gives a better chance of winning if a rider does not have to win instead of winning.
Still, strange things can happen in horse racing, I have seen horses win in play that had odds of around 100