In free range groups the senior hens teach the younger hens how to survive in that environment. The rooster if there is one is the focal point but not the teacher. Young rooster get taught by the senior hens as well.Why does free range change it? Mine are half way between, not fully free range, but certainly not enclosed.
So it's about free range group stability and learning. The senior hens in all the tribes I've known have played a vital roll in tribe cohesion and safety.
The next thing is as has been mentioned that pullets tend to make a nicer meal than senior hens. For many free range keepers a multi generational group has proven to be the least stress for keeper and chickens.
Then there is the factor that one gets to know the chicken better, the longer they live and should one ever wish for the hens to sit and hatch it all goes a lot more smoothly with senior hens ina stable heirachy.
One doesn't really know much about a pullets temperament until she's been laying for a while so it can be a case of better the devil you know. The same applies to roosters.
It's a question of how free range when ranging your chickens are.