Many thanks for all the good suggestions regarding the return puzzle. Here are just a few of the many ideas that I received. My apologies to those not mentioned by name.
Mark Garbowski stated one thesis very nicely:
Demand forced the Sears catalogue to offer easy returns because people were buying things they could not see or touch. Back in 1895, I suspect this was a pretty unusual experience. If you go to a small local shop and know the owner, you probably have a good opportunity to inspect the merchandise before purchase, but this was not possible with mail order. Generalizing, I would opine that the combination of a significant rural population spread over a vast geographic landmass, together with improved communication and transportation, allowed those rural people the ability to purchase (at least occasionally) high quality, exotic (meaning from far away) goods to a degree that was never before possible, and never duplicated in Europe. Before a consumer would send a check or hard cash in advance of receiving an item he or she had never seen or touched, it became necessary to develop a good return policy as insurance.
I suspect that the economies of scale you discuss allow the insurance to be economical, but did not drive its creation. I believe it is a demand side creation, but based on historical circumstances, and not current class or income circumstances. Once the demand side forced mail order retailers to offer it, consumers discovered how much they liked it and forced other retailers to follow suit, even though it was not as necessary.
Ian MacCleod and others mentioned that retail trade in Europe is organized more often on the boutique model than on mass retailing. Salespeople don’t turnover as often as in the U.S., they spend more time with the customer and they personally represent the product to a greater extent. As a result, returning a product can be seen as an affront.
Adam Shostack writes that the credit card companies often reward firms that offer easy return policies because it is less costly than handling a billing dispute. Credit card usage is much lower in Europe thus supporting the theory.
Tim Worstall points out that there are legal restrictions in much of Europe on things like “as is” sales. Similarly, there is a large wholesale market for “as is” items in the US but not in Europe. Both of these factors make offering easy returns more costly. Of course, these differences may be as much “caused by” as “causes of” differences in the return policy but its useful to remember that there is a whole web of practices involved with easy returns.