A queue gives equal places to people with unequal amounts of spare time.

A rule can be perfectly even and still land differently on everybody. First come, first served treats an hour as an hour, which quietly favours whoever has an hour to give, and takes most from the person with a shift to get to, a child to collect, or pain that makes standing costly. The fairness is real and it is only fairness of a particular kind.

If you run anything with a queue, provide a second route: an appointment, a callback, somewhere to sit. And if you have time to spare in a line, offering your place forward is a small correction you can make on the spot.