Aidan, I think you'd need to speak to those who've actually hunted, but my recollection of people I knew who did was that novice hunters, were treated carefully by their riders. They weren't put over all the obstacles, where there were any, and they weren't taken out for a full day's run until older, fitter, and more experienced. As for the standard of the riders - of course they'd be varied (just like jockeys are), but as they've generally bred and/or own the horses they're riding, they are hardly likely to risk them in the same way that a jockey might over-push a chaser. They want to use their valuable hunters for many, many years, and they're chasing a fox, not the hope of prize money and pots.
Additionally, the Hunt Master is there to oversee the proper protocol of the entire hunt, including how people are behaving towards their horses. If they thought that someone was likely to disrupt the hunt by having an unsuitable horse, they'd be told to stop hunting, go home, and not to come back until their animal had improved. Novice riders and horses, by the way, are always ridden to the back of the field, so that they don't get in the way of the schooled hunters and the experienced riders. It isn't some mad free-for-all!
I'm not an apologist for hunting folk, by the way, but I think you've got to know a bit about the way something actually works when comparing it to NH .
