You don't understand it because you don't personally have strict criteria for companionship.
Are you an 80 year old woman who flies six times a year and wants to bring her dog literally everywhere with her, where it will be expected to at worst tolerate and at best enjoy the attention of everyone from grandchildren to the hairdresser, but wants minimal grooming, healthy knees, no brachycephalics, and no more than 20 pounds, that she wants to raise from a puppy?
Are you a family with three kids under 12 years old who spend some weekends camping and hiking and other weekends consumed by kid's activities, so the dog needs to be able to adapt easily to varying activity levels, is biddable enough for all family members to work with, can attend softball/soccer/whatever games, and has good odds of having good hips and elbows?
I truly don't understand why getting a cross bred companion for those criteria is any different than getting a cross bred sports dog. "Just" pet owners have every right to be as choosy about exactly where their dogs are coming from as anyone else, I don't like the "just go to the shelter!" mantra because some people do not like the unknowns that are inherent in getting a dog whose breed you might not even have a clue about.
The point I will concede is that there aren't nearly enough breeders doing cross breeding for companionship thoughtfully. But up here we have some doodle breeders who aren't just slapping random dogs together and their dogs are amazing and lovely, I would get one in a heartbeat if I were looking for an all around good family dog without any other specific purpose in mind.