So why is it impractical in the US, but seems practical everywhere else? As I sated in my original posting, checkers in European or South American supermarkets sit. Are you implying that those "damn foreigners" do not know their trade or cannot tell a practical thing from an impractical one?
PS. As I am writing this, another possible explanation comes to my mind - the volume of stuff being purchased. It is much higher in the US than elsewhere, for several reasons, chief of which is the land use. Europeans and South Americans tend to walk to the stores every day and buy only the stuff they need that day. US-sers tend o drive there from the bowels of the suburbs once or twice a week and hoard stuff for longer time periods. The volume of stuff that need to be moved throughout the scanners and into the bellies to the suburban SUVs may indeed requite the extra flexibility that you mention.
I like that explanation - it is materialistic and does not rely on culture and psychological preferences.
Wojtek