Do you ever pay attention to people's feet when they walk? Probably not, because that's weird, but I do. As someone who is almost entirely incapable of making eye-contact with other humans, I spend a good deal of time looking at the feet of the people around me. My social ineptitude isn't the only reason I do this though. I also find it sort of interesting. Everyone has their own little idiosyncrasies, and I think you can learn a bit about what a person is like just by the way they walk.
I remember when I was a kid my dad told me that the Native Americans could tell the difference between their own people's footprints and those of the settlers because the settlers' feet turned outward when they walked, while their own pointed straight ahead. I'm not sure how he knew this, or even that it's necessarily true (my dad thoroughly enjoys fucking with people's heads, and I was an easy target when I was a kid). Anyway, I remember thinking at the time that white people were kind of awful and all they ever did is fuck everything up, so I didn't want to be like them. I wanted to walk like the Native Americans. So I started paying attention to my feet when I walked and trying to make sure they always pointed straight ahead.
It got to the point where it just happened automatically. I've been doing most of my life without even thinking about it. Now from my extensive research into other people's walking habits, I can tell you that I am one of very few people who do this. I think this may be art of the reason I'm always inadvertently leaving people behind when I try to walk with them. My way is a slightly more efficient.