Idk, but it could be because the payment of the delivery is done 'via surname' to the postman when the package is handed over. So the bank can't track on what you spend your money on (in case you are afraid they do). This option exists at least in Germany. However, it costs an high extra fee.
It's called "per Nachnahme", C.O.D. in English. You'd pay the postman for your parcel and the post office would pay the sender. It used to be quite popular in pre internet days. You whippersnappers wouldn't remember. Not used a lot any more these days.
In my experience, if a seller in Germany offers that option, it's 5 - 6€ extra, I don't know anyone that ever used that service. Probably was more common before online payment was easy.