I owned a horse that was bred for racing, it was 6 years old when I got it. Nanosecond, beautiful Kentucky-bred ginger ninja, with Breeders Cup eligibility certificate. However he wasn't fast enough as a 3 year old on the flat - one win, 2 seconds, a third and a number of also rans. So he was put to hurdles, where he threw the jockey a couple of times, no places; so he was put to steeplechase where he threw his jockey on every outing. He failed because he hated weights heavier than 7st on his back, but it took me, an amateur owner, to spot that pattern in his race form. He was passed through several trainers who probably treated him well enough, but failed to understand the horse, so he ended up sold to a woman for showjumping who was also thrown a few times and then he was just left in the field unridden for 6 months. Sadly I had to pass him back to the dealers as I was too heavy by far and my wife couldn't handle his energy.
My point is that racehorses may be treated well in stables but they are just used to make money, and when that fails, they are regarded as expensive indulgences and got rid of unceremoniously. Many a racehorse has been shot for an injury that isn't life threatening, but makes them worthless to a stud or trainer. Many a horse has been driven over fences that are way too high, or races that are too long, in the HOPE that they fall and can be shot so that insurance pays out. I know this for fact, from an erstwhile pro jockey friend and having seen it done myself.
So I have lately become set against national hunt racing and Aintree festival in particular. 3 horses died this week at Aintree. Just so that a bunch of people could make some money.