and chicks are often even tended by 'aunts and uncles' who are currently chickless themselves but willing to help out a little one.
I noticed this in my flock as well. I only had co-broody hens a couple times, but i do see how my flock has gotten used to putting up with hormonal broodies and gives them space. They're also very accepting of young chicks. My 7 yr old EE hen can often be seen near the family and sometimes even tidbits. We jokingly called her "Auntie" b/c she visits for a little while but also leaves and does her own thing. She has never gone broody in her life; she's just getting soft in her old age.
I also noticed that when a rooster calls an alarm or a sudden noise is heard, the chicks will quickly take cover under the nearest hen - not necessarily their mama. For a few moments until the danger has passed, the hen will shelter the frightened fuzzy.