We have fire drills here at Canterbury once per semester to make sure that folks know what to do when the buzzers ring. Very annoying, and it’s pretty unclear to me that they do much to improve preparedness (what’s so hard about walking down the stairs anyway?)
I agree that fire drills don’t do much to make people better at exiting buildings, and any minuscule improvement certainly wouldn’t be worth the inconvenience of regular drills. I suspect, though, that they do lead to a significantly safer and more orderly exit in the event of a fire. My folk understanding of fire safety (which I can’t be bothered confirming) tells me that panic and the possibility of trampling are greater risks during a building evacuation than dawdling. By making a genuine fire alarm seem like an annoying demonstration of concern for health, fire drills keep people calm in the event of a real fire.
The ostensible purpose of fire drills is to make people more aware of the possibility of fire, which is supposed to make them safer. The real effect is to make them less aware, which in fact makes them safer. I’m sure this is entirely unintentional, and I suspect real fires are too infrequent to make the improvements of safety from drills worthwhile.