but, to answer your rude questions: First, you have a way of telling, through reviews, whether a provider will NCNS. If you choose wisely, and you have many, many choices I'm sure, then you cut down on having someone cancel on you. I don't think providers have that kind of knowledge going in.
And, if I were you I'd use an alias so you can at least have some hope of someone seeing you. At least I'm not hiding behind mine being rude.