Not genetics, because you say they are more or less masters of that art, and it would be admitting a defeat if they cannot engineer themselves around that kind of problem. There has to be some other reason, possiblepossibly something that pertains to their nature.
Maybe they think that having dogs, or pets in general, is too childish, a thing that puny humans do - having one is like an adult sucking on a pacifier, or an adult playing with a doll.