The ability to hatch eggs is not well appreciated among the general public. I was discussing it with a journalist who was unfamiliar with poultry the other day. She didn't realize that the production Leghorns and Cornish-Rock crosses used in industrial egg and meat production are unsuitable for small flock ownership because they can't reproduce themselves. In sustainable agriculture operations and developing countries, being able to renew the flock without having to buy more chicks is important.
Broodiness has long been bred out of Leghorns. Broody chickens stop laying eggs for the duration, so it's economically undesirable to single-focus operations. Cornish-Rock crosses are bred to eat and grow until they die. They are physically unable to breed because of their large breasts and ungainly legs. They are the first generation cross between two different breeds and as such, will not reliably pass on their characteristics. A second generation would be a mix of characteristics.
A traditional breed such as the Dominique can mate naturally and the hens know how to set on the eggs until they hatch. They retain the instincts to care for their chicks and teach them how to find food and fit into the flock. These invaluable qualities distinguish them from industrial breeds. Traditional breeds are a valuable part of an integrated, sustainable operation and a requirement for productive small flocks in developing areas.