^All these people are really in the way. Inconsiderate sods.
Stairs. You know stairs. The non-moving escalators. The ones you reluctantly drag your animated corpse up whenever the lift isn't working. Yeah, you know stairs. They're pretty essential to every day life, provided you're not a lonely hermit in a bungalow. And if you are, bully for you.
Stairs are usually just about wide enough for two rows of people to use them, one row going up and the other, surprisingly, going down. So, what happens when two members of these rows recognise each other and they wish to converse? Why, they stop and talk. On the stairs. In the way of every one else who was currently using the aforementioned stairs. And so, everyone has to stop ascending or descending the stairs as Joe Knob-Gobbler and Jamina Pig-Features discuss the intricate ins and outs of just how drunk Steve Statitis got last night. It's not like you're in the way or anything, is it?
This entire debacle can be made worse, however. Specifically, on double-decker buses in London. There is nothing worse than someone waiting at the top of the bus stairs, waiting for someone to vacate the upper-deck so they can grab a seat. Think of it like this; when someone does leave their seat, they need to go downstairs. But they can't go downstairs, because you're in the way. There is barely any space for either party to get past each other because this is a narrowly confined bus. A stalemate occurs when seat-evacuee and seat-grabber can't get past each other, because the latter party thought waiting at the top of the narrow, confined, tight, uncomfortable staircase was a sensible idea. It wasn't. Wait at the bottom of the stairs like everybody else, you twunt.
Basically, it boils down to this. If you're on the stairs and you're not moving, I will rectify that by pushing you down them.