I believe a compass is a "must have item". I have been in urban disasters where the local landmarks have been destroyed and the whole place seems unfamiliar. It is very easy to get disoriented and move the wrong direction. This is not a good idea.

Even in normal life, exiting from an underground train station into an unfamiliar city can be very confusing. I carry a small compass and can easily check my "intuition" and quickly orient myself.

The magnifier on the compass is probably used to read the fine print on some maps. I doubt that it is for fire starting as it is a pretty small diameter.