@bloodline (& others)
I've used at least one (and am a member of a) co-op.
But believe me, it's definitely not socialist.
But my theory is certainly not wrong, however. Well, not entirely, anyway.
Thoughout the past 100 years or so, socialist "supermarkets" or food shops really did not have much that people wanted. But they didn't have an awfull lot of what people didn't want, either (except perhaps, empty space...).
:-)