You order a shirt online here, a facial cream there. You pay two different companies that in turn instruct (two possibly different) mail services to ship the things to you and you will receive the parcels separately, probably on different days. The environment suffers, and you might have to go twice.
With this new service, let us call it, Efficient Post (EP), you can have the stuff sent to you together. You will pay less for the shipping and will have to go to the post services once only (or they come to you, whatever). You MIGHT have to wait one day extra, but you will do the environment a favour and use less resources for sending/shipping/transporting.
It is perfectly possible to do. Klarna, a billing company in Sweden, managed to make many companies to outsource their billings - so it is kind of a standard service now. Let us do the same with the shipping when possible.