You expect the drive to forensically inspect each can? Your lips have been around the top of it, it's a waste product that's potentially contaminated and can't go back in where other peoples shopping is. So where does it go? I can't ever see supermarket delivery drivers taking peoples recyclables back, just too many problems.Regarding space; I can't see how a load of empty bottles & cans takes up more space than the entire food delivery you're getting at the same time? (Unless you order 10 crates of beer one week and a sandwich the next). Our deliveries always come in bags inside plastic boxes, which would contain any leakage, and it would be easy enough to enforce a condition that they must be clean and any dirty ones won't be credited.
Yes some people might be going there anyway, but it's still a tedious task of bagging all the cans, keeping them by the door, then when you go shopping, put them in the vending machine one by one. All this for the exact same result as what we currently do.People already either make that journey to the supermarket to shop, or have their shopping delivered at home. Done properly*, no extra journeys are required. Easily solvable problem.