As you have noted, some hens are better at it than others, by hatching eggs of hens that are not good at it, one gets hens for the most part that will not be good at it either, and less and less broody, in the wild, that strain of birds would go extinct. However, in animal husbandry, one can artificially raise those animals for a trait that we want, more consistent egg laying. (However, not fool proof, my first broody was a hatchery left over chick that turned out to be a Cornish cross, and they are NOT suppose to go broody, She was an excellent mother)
Interestingly enough, my husband wants good mother cows. Cows that do not bring in a calf, do not stay in the herd, they calve on their own, get that calf up and nursing on their own. Do not go out into the pasture and try and grab one of those calves, they will eat your lunch. However, that is what he wants, good mothers, do not let coyotes or mountain lions eat those babies either.
Animal husbandry is an old, old business, and kind of interesting.
MrsK