I remember at a seminar in 1995 I asked how to correctly slide the foot across the floor during the walking kata. Sensei then gave a lecture about how the foot moves just slightly above the floor during the steps of the walking kata. Although he taught this, the group went immediately into practicing the kata and all I could hear was the dragging of feet over the mat. I am not saying Sensei was not doing what he was teaching, I am saying no one else apparently listened!
These slides and grinds of the feet into the mat are friction. Friction in mechanical motion is inefficient and indicative of wasted energy.
I am not promoting any way to do the walking kata, it is for the student of the art to decide. I would like to suggest doing the walking kata under test circumstances to see where the friction points are.
Put on your tennis shoes. Go outside. Find a nice rough concrete driveway. Perform the walk in tennis shoes on the concrete. This exercise will quickly draw out any flaws in the efficiency of your stepping form. Feeling brave, think I am crazy? Now take your shoes off and practice the walk barefoot on concrete. The little red marks spouting fluid will more clearly demonstrate the evils of friction in the walking kata.
If you are unwilling to go outside I have one last exercise. Try doing the walk silently. No *vip vips* as the feet drag across the mat. Be like ninja!
Moral of the story, quit dragging your feet!