My colleague Mark Bils figured out a way to rephrase this so that even an economist can understand it. Every producer knows that workers should spend less time with inferior machinery. Compared to an escalator, a staircase is an inferior machine, so the "workers"—that is, the people who use the stairs—should try to minimize their time there. The way to limit your time on a staircase is to keep walking until you get to the end.
The same argument proves, incidentally, that even if you choose to walk on the escalator, you should always walk even faster on the stairs. If you're planning to write and tell me that in fact you walk at the same speed in both venues, I'd really rather not hear about it right now.
So what's the moral of the story? To me, the moral is that we should take seriously what we tell our students: Marginal analysis really works. If it seems not to be working, the right question is not, "Why doesn't the marginal analysis work?" Instead, the right question is, "How am I failing to understand the marginal analysis?" or, more succinctly, "In what way am I being stupid?"