@lazy gardener
You folks are not getting my points at all. I have no problems with assertions that hybrids perform as well as purebreds in terms of productivity, fertility or longevity. What differs is the value of the hybrids in the eyes of other people. You are correct about how heritage breeds are developed and by now better know I understand the concept based on work with American Dominiques alone.
Look at it this way. In my area which it appears to be typical, roughly 10 households have keep small flocks of chickens during the last decade we have lived here. My family represents one of the households. Every single household outsourced birds at least once during that interval. Those without roosters had to outsource for all replacements. About half of the flocks are hen-only. Some birds aged out based on egg production decline. Most where lost to depredation whether free-ranged or not. More than once I could hear a neighbors flock being destroyed by predators at night. A couple parties completely replaced flocks owing to depredation losses more than once. Most kept flocks with a variety of breeds for the purpose of eye candy. Most offspring produced where hybrids, Most house holds, even when they had a rooster, did not produce chicks. Of those that produced chicks, most did not produce enough chicks to make so they did not also outsource. A few people did sell / give away chicks but those transferred birds where generally not as highly regarded as those purchased directly from a hatchery or breeder.
The pet concept did little more than extend the time required for a bird is replaced by an outsourced bird, hence the paper towel analogy.
If people in my area where not able to outsource chickens, they would either run out of chickens in just a few years or as a community, switch over to breeding more and sourcing locally. I am one of the very few in my area that has a flock that can persist without getting birds from the outside even during a brief 10 years at my present location.
To develop a landrace, you must be able to maintain a population without having it swamped by imports / immigration during the time it takes for a locally adapted gene complex to adapt. Look back at how the Icelandics were developed. Very little if any genetic contributions after population was founded. There flocks, at least in the scale of a country where self sustaining because all birds where locally bred. Contrast that with US and current situation even in Iceland.