Only one problem ( sometimes) people dont like to pay the extra cost of the packing . It can cost to provide protection, they dont appreciate the time and effort involved in preparing the packing . Not everyone has access to foam and it costs to buy it in and the cost has to be met by the customer. Same as "custom boxes" , i have yet to find a standard box so that different models can be packed economically. I have to add that U.S carboard boxes are by far superior to U.K boxes. It is hard to find twin wall or triple walled boxes here and the single walled boxes are so flimsy that double boxing is required and therefor adding to the final shipping weight.
Most modellers who sell their models know this ,but "joe public" don't appreciate what goes into providing a safe package . All they want is the price of a stamp to ship.