Dogs end up in shelters for only one reason - they were not purchased through reputable breeders. There would be no need for shelters if all dogs came from reputable breeders, because the breeder would be taking back and re-homing.
In my breed, it is not uncommon to NOT have all the pups spoken for before a litter hits the ground. As long as the breeder is willing to take care of the puppies in the event they don’t find a buyer, then what is the problem? They often have multiple show quality pups from the same litter that they don’t mind keeping. It is a very high labor, little sleep breed to raise, so most do 1 maybe 2 litters a year tops.
As for impulse buying, many here would consider both my show dogs to be impulse buys. Once I decided I wanted one, I didn’t want to wait a year or more if I could find one sooner. When I started looking for a show puppy, I think it took me about 2 weeks to find one. My friend in another breed helped me evaluate her. She finished, owner handled, in 4 weekends of showing with 3 majors, including a breed specialty.
When we lost our last girl (her daughter), we were very distraught being dogless for the first time in 20 yrs. I went looking again. Within 2 months, I found quality puppies available, from 2 different litters. The puppy we bought was already 11 weeks, so I could have gotten her sooner if I had found her. I am thankful every day that I have her. She is both big and correct.
My cousin just lost her boxer. She was very distraught and didn’t want another dog. after a couple of weeks, the house felt too empty, and she decided to get a puppy. I don’t think she is evil for not wanting to wait a year for one. She tried to go the rescue route, but they denied her, so she ended up putting a deposit on a puppy from a breed she always wanted from a litter nearby. I consider the breeder to be irresponsible by my standards. It is a farm that breeds livestock and LGD - as far as I can tell, no health testing or take back clause, which is where I personally set the low bar. She has never bought from any type of breeder before, and I wish she found a better breeder, but my point is that she is not going to dump said puppy because she didn’t wait X period of time for it. That is like some breeders in my breed saying that they won’t sell for less that $XXXX, which is more than the going price for a quality puppy, because they believe that if you don’t pay that much, you won’t take care of the puppy.