For some it's a very bad habit that they don't even realize they're doing. I confess I used to be one of those people, but I'm consciously trying to reform. Tripping over cracks in the sidewalk, falling flat on my face a few times from (I swear) tripping over my own feet. Now I sometimes talk to myself when I walk (under my breath), "Pick up your feet, bend those knees." Dragging your feet when you walk can be very dangerous-that sidewalk's hard when you fall!