It doesn't mean they socially know everyone that shows up, but every member would have paid some amount to buy (a) share(s), at least that's how coops work where I am. Plus accumulated dividends. That's a relative barrier to fraud if they decided to issue credit to members.

You could still fraud hit them in this circumstance, but they have some kind of info printed on your card with your name on it and how long you've been a member, and somewhere in the background, a phone# and address.

If one wanted to commit retail crime, easier to just take stuff and walk out without paying.