and not be held up with loading empties
...
Empty bottles perhaps not, but empty roll cages and totes and pallets and recycling and returns... And that's whilst working around the remaining deliveries and keeping the load balanced
Why are you making fun of that?
You are the one speaking without knowledge. Believe me the handling of the cages and pallets being returned, even when loaded with returned product or recycling material is nothing and does not take long at all. Even with a full 20 cage and pallet delivery it takes 15 minutes with experienced warehouse staff, to take it all in, and send back the returns. They roll off and on, with pallet pump trucks moving the pallets stacked high.
The handling of crates of glass bottles, running into thousands for a fair sized store, would however take a lot of extra handling, and as they would have a value, require checking. I remember when a dozen medium sized (Corona, R.Whites, and the like) would be packed in a plastic crate, and even stacked 5 high would be awkward to shift, usually on a sack truck. Now, if 2ltr glass bottles were transported, away from their original factory packaging, in the thousands that a store could take in from customers returning in the quantities they now buy them in (totally different than the 1960's), then it will take extra storage space in stores that do not have that now, extra manpower to handle them, and conceivably, a separate truck to transport them away from the store back to a CDC (who would then have all the handling and storage issues repeated). Even if the drinks producer has a truck specially to take the returns back from the store, there would be still the extra storage, handling and transport costs. For the producer taking back the empties, they would have to have new plant to wash, inspect, and re-commission those before being re-used.
All the way along the line extra handling costs, plus all the others, would be involved. The only answer to that would be to smash the return bottles when they come back into store (like the cans returned are planned to be crushed), but then industry has the problem of handling even more recycled glass, with all the extra transport and plant costs.