You would if you lived in a country where merchandise was available infrequently. Stores often were empty of any wares - so fish store is empty of fish and meat store is empty of meat. ;)
There is another level of nuance in the joke though. You need to have had spent some time in a Eastern European country. Everyone is a stickler for rules, details, and knowing the "correct" answer, even if in practice, in a given situation, it makes no difference at all.
This joke brings out that quality very nicely.