I think that there is some cultural difference behind this trend, but also just how people were brought up. I was raise din a house that was constantly being worked on (it was gutted and rebuilt slowly, so we lived there through much of the contraction). With a dog in the mix too, it just wasn't a good idea to go barefoot all the time. We also had hardwood floors that would sometimes splinter. Now I am in and out of my house so much during the day, I forget to take off my shoes. But I imagine it would really help in keeping my house cleaner!