They possibly do but surely thats better than having it trapped between the leather and your foot (wet sock). sorry to keep posting links to other sites but if you look at tip 6 this guy says having a plastic bag under your socks is the best way to keep your feet dry (this probably only works when its really cold)
http://www.ukhillwalking.com/articles/page.php?id=6903
Back when I was a motorcycle courier in London I would regularly see a guy riding around with his feet in carrier bags, held in place by bungies. His bike was worth a few grand. Each to their own eh.