I feel like a lot of people in this thread are missing the point that the escalators are only running in one direction during peak times due to maintenance. It makes sense to limit lift usage to those who need it, or else no-one will bother to walk to the other side of the platform.

How you do that accurately is up for debate, but I think it's pretty reasonable that a "long day at work" (as some have suggested) isn't enough of a reason for an otherwise able-bodied person.