The sad reality is that the supply chain from farmer to whole sale to grocery store is incredibly optimized but the way back isn't. You'd have to check every single item if it is safe to eat or not.

Also, the bigger grocery stores like Walmart are basically a warehouse for food with checkout. There's bound to be some (process induced) waste. It's how the stores are set up.

There was a Zeit article about reporters putting a GPS tracker into shoes they RMA'd. The shoes were "recycled" immediately. They can't sell RMA goods as brand new even if they are barely used. If they did, then some customer will give them a bad review and ruin the brand.