I've personally had too many issues with hens screwing things up for me! I'll give a broody the eggs I want her to hatch and she'll kick those out of the nest, or other hens will jump on the nest and lay extra eggs messing up the hatch time. I've tried marking the eggs that were all set at the same time, and before I know it all of those are gone and there are entirely new eggs on the nest! Some hens are really lousy mom's. Some will eat eggs, others will set on a nest until just days before hatching and then abandon the nest!
I've only had one hen successfully hatch an entire clutch of 10 eggs, because she was secluded to the hayloft in the barn. She's also a mixed OEGB and silky cross, so she's a super good mom! But... I had another hen (my favorite) try to hatch some in the same spot. I figured all would be just fine. A predator got her.
Killed her, didn't eat her or her eggs! Up in the hayloft too! So that is not a safe place for broodies anymore either.
The hens that try to hatch in the henhouse on their own usually end up with a bunch of unhatched eggs, only able to hatch three or four before getting off the nest and abandoning the rest.
I've had hens discriminate against eggs that weren't their own. When setting on a communal nest or setting eggs that I placed under her, she would kill the babies that came out of different sized or colored eggs than her own! She would only raise her own chicks!
I know a good broody is better than any incubator, but I've had so many hens mess things up! If I don't care what or when the chicks hatch, I'll just let them go and do their thing. But if I have specific eggs I want hatched, I do it myself, or I seclude the broody and keep her safe from the other hens so she can do her thing. That doesn't always work either, some broodys don't like being confined and will abandon the nest, just to go off to another unsafe location to start over!
I guess I like to be able to control the situation, especially when the eggs in question are important to me!