"Designer Dogs" - The Various Poos and Doodles - What is the Basis of Objection to Them?

I, too, am amazed that someone would pay $1000 or more for a poodle crossbreed. If crossing with poodle improves so many other breeds, why not just get a poodle to start with? That said, what is the nitty gritty basis for dog people objecting to the practice? Is it decreasing the market for their purebred dogs? Is it a desire to charge as much for a pet quality purebred as these bybs are getting for a mutt? Is it the misrepresentation of these crossbreeds as a legitimate breed, when we know they do not breed true to type? If the general advice is to get a mutt for a pet, then why do these mutts not qualify as good pets when a Heinz 57 does?