Escalators are an interesting first world phenomenon. While not strictly necessary anywhere, and taking more horizontal space than an elevator, they still turn up all over in most first-world countries. The key to their popularity is, no doubt, the fact that they move traffic much more quickly than an elevator that has to stop and go, and offer the option of walking while on them to increase speed to destination even more.
One thing about escalators is, they’re always either going up, or down. Not something you see in an elevator that changes direction with each trip.