Chickens are social, but they vary in their need to be in the social mix. For some, it's enough to be in proximity to the others but not to have direct contact.
Humans are also considered social animals, (some even say "herd animals"), but while some feel the need to always be in the midst of human activity, others are "contemplative" and need only occasional human contact. So it can be with chicken individuals.
I have a Speckled Sussex in her own coop and run that can't stay out of fights when she's permitted to free range with the others. One of the roosters hates her so much, he's torn her up pretty badly in the past. She has a friend who lives in exile with her, and the two get along very well after the Sussex totally beat her up and declared victory by crowing three times.
The two may appear to be lonely, but they are in full view of the flock and can communicate through a common barrier when they feel like it. For some chickens, this is plenty of exposure to the flock to give them the sense of well being chickens derive from other chickens.