They wouldn't do it if it wasn't profitable! we make our own problems.
Any breed will suffer when it is altered. But wait a minute... hasn't man been altering breeds to match his needs for hundreds no thousands of years?
All the breeds in the akc were made by people who had to fill a need and altered and mixed breeds to fit their need. Hence sporting class working class and other. I do not condone runt breeding it is just plain wrong.
However to say breeding down size has to be done only in a bad way is just a lie. If people didn't cross breed we would all have great Pyrenees and Tibetan masstiffs as these are two very old breeds who have both contributed to many blood lines.
The AKC does not breed dogs they just confirm blood lines, they also don't check health of registered dogs so unless you plan on showing your dog in there show I would rather count on my vet to check my puppy then their registry. They also only list 172 breeds out of over 300 breeds world wide!
My point being get what you want not what people want you to have. I have 4 Shih-Tzu and they are all over Two year old and rescues. My biggest (Sprokit has huge eyes that bulge) he's is close to 18 pounds while my smallest Aja is only 5 pounds ( she is on this site) and she is the most perfect little Shih-Tzu. Her only illness in two years was a tape worm as a baby.
So I say every dog should have a home. Take your time and rescue. If you don't create the market they won't do it. Rescue if you take your time you will find just what you want big or small.