Do you remove your shoes before entering your home, or wear them inside? Removing one's shoes is a sign of respect to the house, and is a deeply ingrained cultural habit throughout Asia. It is likely a practice that billions have (if you consider China, India, and Japan alone), but may be less common in the U.S. - nevertheless, I know many in the U.S. do remove their shoes - including at least this ASU student, whose shoes point toward campus. I've seen the subject debated, and it seems silly to me. I mean, if you want to wear your shoes inside, more power to you. And if you don't, great. In my opinion, the argument not to take shoes off, however, is a bit weak when you consider the overall benefits of taking them off. It almost seems a bit mindless to leave them on, with the exception of those who leave them on for some purpose (maybe they need arch support?).
Consider this: shoes are dirty. They are that thin bit separating you from everywhere you've been. You know where you've been. And on your travels things stick - lead, pesticides, oil, dirt, public bathroom floors - all deposited on your home floor to become part of the indoor air that you breathe.
And then consider that removing one's shoes can be a mindful practice - each opportunity to do something even as simple as removing shoes can bring attention to where you are, right now. Your bare feet touching the floor - whether natural fibers or the smoothness of wood - is an entirely different connection than your shoe touching the floor. As someone famous once said, "the foot feels the foot when it feels the ground."