Specifically while doing this exercise, I imagine that the additional padding and weight spreading is more comfortable than doing so barefoot, since the goal is to create lifting force between the floor under your your feet and the cable via your hands. I also imagine that many astronauts do frequently "kick off" objects and walls to start their propulsion/movement around the space station.
More generally - I often wear socks and slippers around the house while otherwise half dressed, because my toes get cold. Warm feet is a luxury.
