They dont fly freely.Mine did, just not very far.
The natural "ur-chicken" is a social, forest-dwelling bird. Living in a flock, and being well insulated, it has no need to fly very far: they don't migrate, mammalian predators can't fly at all, large avian raptors avoid dense forests, and small raptors (even dogs!) avoid fighting with cockerels. But it does need to sleep off the ground and to take off quickly if attacked by a mammal. So it has evolved to fill an ecological niche.
The domestic chicken is an odd creature in many ways. Most birds lay eggs once or twice a year in a distinct nest and sit on them until they hatch but the free-range farmyard chook lays an egg every day, not always in the same place, and only gets truly "broody" and sits on her eggs once or twice in a lifetime. That said, the bird has been bred to have very large flight muscles (the white bit) and carries very little dead weight (leg bone), so is still capable of rapid takeoff in any direction, even by running downwind (unlike soaring birds).
Horses for courses.
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