Why would they invest in it? There's no money in it, there's billions in football. There's no interest in it from those who aren't already horse owners, it's a completely inaccessible sport to the masses due to the cost of lessons and the huge cost of actually owning unless you are already well off and have land, so it will never get the engagement that football would get where you can go to the local club and pay £5 per session. Not to mention the bad PR from many people about using animals in sport in the first place. TV is business, horses don't have profit anywhere near them unless it's racing.
Sometimes you have to look at things objectively before you get angry about them, and you are thinking about this from the POV of being a horse owner.