Abigail Zuger in The New York Times:
Take what must be the greatest cheap medical fix in all of history: the bar of soap. Soap never stops proving itself. As recently as 2005, a study from the slums of Karachi, Pakistan, showed that free bars of soap (and lessons in how to use them) cut rates of childhood killers like diarrhea and pneumonia by half. But you don’t find soap in American hospitals anymore, at least not in its classic solid rectangular form. A variety of expensive improvements have replaced it, all created in response to the various ways in which modern doctors and patients reflexively undermine good, inexpensive tools. First, we automatically capture these things for our own personal use: Bars of soap left in any public place are likely to disappear in short order. (That is why toilet paper rolls are generally locked into their little metal houses.) Second, we find fault with them. People will actually use the observation that bar soap is “dirty” as an excuse not to wash their hands. (Studies have shown that you will not pick up somebody else’s germs from a piece of soap, however dingy it may look.)
More here.