Horse Racing

I have been educating meself on horse-racing and have discovered that it doesn't seem to be such a nice sport. This was initiated by a news article about the second place winner of the Kentucky Derby, Eight Belles, who was euthanized on the track after breaking both front ankles. I learned that horse racing is incredibly dangerous to the horses, akin to dogfighting (which, I believe, is banned for being too dangerous), that their spindly legs aren't built for racing down a track with a person on their back. (who also whips them *glare*) So why do it?
Another aspect I don't fully understand is the fact that when a horse breaks a leg it is pretty much a death sentence; they are often euthanized once discovering the injury, like what happened to Eight Belles. However, I was under the impression that a leg injury in a horse is a huge pain in the butt and majorly expensive, as the horse needs to be put into a sling to prevent them from putting weight on the injured leg(s). The process often involves putting the horse, in the sling, in a big bucket of water to allow them to still exercise their legs. My new knowledge tells me that horses have little blood flow to their legs which makes them slow to heal and quick to get infected but I guess my question is, if there is a waym, (and I believe there is, and if you really care about the animal you will do everything in your power to help them) why not? These horses earn their owners scads of money when they win these races, so wouldn't it be expected to pay them the respect of the best care possible?
Sorry, I am done now, just a wee rant.
Hermit