I think the reason it's a thing is the same as the reason Hollywood exists and Las Vegas exists. Overabundance of inhumanely rich idiots that are bored and want

I think the reason it's a thing is the same as the reason Hollywood exists and Las Vegas exists. Overabundance of inhumanely rich idiots that are bored and want to gamble. And they do because they falsly believe they have an edge in their bets due to their secret knowledge of the game and unique talent in picking the right horses. Most of them will lose most of their bets. But a handful of wins is more than enough to write about to draw in next batch of idiots or even the same idiots again if they still have money to lose.