Where are these hatcheries breeding for Standard LOL? I think they throw a few roos in with a bunch of hens and harvest the eggs, that's it. You can see where in that situation aggression would be a bred INTO them, as the most aggressive roo is the one most likely to pass on it's genes. You can see the cross breeding for egg production, but you are right, they take no real concern for the aggression of the bird. In fact to them roos are a by-product......I have to agree with TarraBellaBird and disagree with Free Feather here - I see no reason to think that human aggression and hen protection are genetically linked. We have no problem breeding livestock dogs that are nasty as all heck to any sort of predator, but still extremely docile around their charges and humans.
That's the short of it.
The tough thing is that most breeders couldn't care less about this - the hatcheries are breeding for standard, and breeding for egg laying (more eggs, more chicks to sell). They don't have to live with aggressive birds.