Why do people stand in doorways?

This is a brief complaining session about something that has bothered me for a long time. Why do people stand in doorways?

It happens whenever I visit any shop. You are trying to get in or out, and there is someone, or two people, or a small group of people, standing in the doorway. And they don’t budge.

It’s not only doorways. It happens at the bottom of escalators and stairways too.

Of all the places in the world, why do they have to pause in doorways? It’s a blatant fact that someone else will be coming or going, so why block their passage?

They are the same people (I am guessing) who block supermarket aisles and shelves, either with their trollies or their bodies. Why?

I bet they linger by the bus door too. Or stand in the way of someone trying to get in a taxi.

Perhaps it is a game.

If anyone has the answer, please let me know.