i'm not sure why this place does, but it seems to turn them over (at prices higher than someone just looking for dinner would likely pay -- plus my two boys are too young to be much of a meal, at 8 weeks) -- just as i was leaving, another woman had pulled up with roosters in her trunk.
but they sell a LOT of birds, both genders -- not only little chicks but they're constantly getting mid-sized pullets and they always sell out incredibly quickly, of everything (also ducks, doves, rabbits, etc.) -- one of my former students works there, & she says everything always goes super-fast. Sonoma County people just want their critters, i guess!