It sounds to me that the walk/stand system is nice because it creates a priority queue. Some people would rather wait and stand than not wait and walk. The peop

It sounds to me that the walk/stand system is nice because it creates a priority queue. Some people would rather wait and stand than not wait and walk. The people who are in a hurry get to walk and not wait. If the norm was "always stand", the 40% of people who walk would be much more annoyed. Even when the escalator was only at 5% capacity, there would be enough side-by-side standers that they wouldn't be able to walk.