Many of these were set up in areas where there are no employees as well. While some may be "vending machines" by definition many colleges and work sites installed areas with food/drink items all set up on shelves where you can go and grab what you want and then go self checkout on your own and walk off. Cameras and recognition of who is taking items without paying has been the regulating power since they were set up. Many do not accept cash, and you use a card, your phone or even set up an account using your fingerprint to grab a banana/cookies/gatoraid/ice coffee/whatever and pay quickly. The idea that they knew who you were was used to balance their costs against the number of lost/stolen items.

It is foolish to think they weren't identifing individuals, but it would be wrong to sell the data as well.