Why is a barcode called a “proof of purchase” even though it’s there before you purchase it and remains whether you actually purchased the item or not?

Question

Basically, the title. Why is a barcode called a proof of purchase, even though it’s usually printed on the item and is still there even if you have stolen said item?

In: Economics

Answer 1

It’s physical evidence that you acquired the product (hopefully purchased, not stolen). Think box tops for education. They don’t care you purchased a specific box, they only need evidence that you bought A box.