Genetics, Yorkies didn't just naturally evolve neither did miniature schnauzers, I have one of each and a Schnorkie To lend my response to why purposely breed them...hmmmm it's the purposeful and intentional controlled, recorded and planned crossing that are supposed to qualify as "designer dogs" the term hybrid and designer vary in a hybrid is a 50/50 a designer is supposed to be a 75/25 I have a Schnorkie (his DNA results actually list him as being 62% schnauzer and 37% Yorkie with a 1% variation unknown) he's a freakish result of hybridization-he's 21 lbs (the growth inhibiting gene can get "shut off" i.e. Ligers etc) has a quadruple color coat that is the result of a salt and pepper mini schauzie and black and silver yorkie, he has the body of a deer and a tiny head that makes him clumsy and awkward-he's as stubborn as a schnauzie and as spaztic as a Yorkie- I think he's perfect! Of course I'm impartial-I'm sorry but the picking on hybrids or "designer dogs" isn't nice...how do you think Yorkies came to be? Miniature Schnauzers also...they were all "created breeds...having said that, the whole designer market is a joke though at this point (Canadian Schnorkie breeders are known as the best by standard FYI) and especially from my experience being in California the vast majority of those whom breed "designer dogs" are puppy millers-does anyone really think they are tracking genetics at all-it's sad but true and the fact is you never know what the result of the offspring will be until you get into F-3 and F-3 crossed of hybrid which can have consistently produced pups, however there are many proven genetic benefits in the F-3 production pups, weeding out certain breed inherent defects, crossing breeds to counteract genetic defects and weaknesses etc. (Google it if you want a genetics lesson in hybrids)
Designer Dogs, Hybrid Dogs, Designer Dog, Hybrid Dog this site just explains f-3,so the reality is there is a lot of "waste" pups. In fact my Scoobers was a rescue he was dumped outside a pound in a bag with another "funky" looking designer dog-the pound gets tons of "designer dogs" dumped there all microchipped to "breeder" whom never respond to contact requests-and there is little to nothing that can be done about it. The whole designer breed market (it is literally that a market...a sick one too) here is a mockery to the original ideal of it...then again saying weather the ideal was from accidental crossings or from intentional manipulations at this point is really saying which came first the chicken or the egg? Well there's my whole dime on the topic...wait and since I anticipate ppl not liking what I said I'll add another two cents...I really dislike Chiweenies...really a miniature badger killer and a spaztic vicious lil dog no one knows how it came to be..then again I don't especially like Doxies or Chihuahuas...I know I'm a Chiweenie racist.