Is it rude to walk past someone on the stairs?

[Helpmeup]

At my workplace, people don’t pass each other on the stairs. If someone reaches the staircase and there is already someone going up or down, they wait at the top or bottom for them to finish using the stairs. I don’t really understand why, it’s very wide and can probably fit 3 or 4 people next to each other, so the space isn’t the issue. Is it considered rude? If so, why?

If it’s wide enough then no. Only when it’s too narrow should you wait if someone is already on them.

My mum used to say it was unlucky to pass on the stairs so maybe they are all superstitious

Maybe they're superstitious, isn't it supposed to be bad luck?