It requires skill, which automatically rules out 99.9% of this forum. No offence.
Though your right by what you said when it comes to it physical gambling, those that will bet on horse riding have to be experienced in it, however when we consider the online gambling on horse riding as well which requires no experience, we don't also have much fans into this because it's not one of the present century games gamblers had love to play, most of the horse riding bets played now are virtual bets and not live match from the casinos and gaming stations, we can notice that there are many factors that affects this category of gambling to be less accepted by most gamblers.
you do not need to be able to ride a horse to bet on it.
I think horse racing is slowing up due to the resources needed to raise horses. Land Land and more land is needed. Belmont Race track in New York has at least a hundred acres of land.
Aqueduct IN New York has 100 acres of land
Saratoga has 200 acres of land
they rotate and used to shut down. Now they have casino's so the land is not wasted.