Why is it a rule in most public buldings to not stand in front or by a fire exit?(open door or not) it makes no sense to me if there was a fire I would just leave like everyone else.

Were I used to work we used to have this rule and the door was always open and me and a few colleges would stand a few feet away from the door, we would get told to move, when I would ask why? The person would always say it’s a fire hazard, I would then ask how is it a fire hazard? but I never got a answer.
We also had a rule to leave everything behind when the fire alarm goes off.
Once it went off and I couldn’t take my laptop what was rid next to me, literally just below my hand…meh I was thinking about telling a good joke but I’ll leave it.