Because if they fail in falconry, they don't starve.
Every year we have hawks and eagles that fail to catch my birds. Some succeed, most don't. Certainly doesn't stop them from trying
No, they'll try again. Otherwise within a couple generations ,you could have a whole hawk population that never preys on chickens. Remember, even hunting 'natural' prey, hawks (and especially juviniles learning to hunt) don't have a perfect success rate. If they stopped after failing each first...