Why is this actually the case?

According to legend, it has something to do with the history of mariners. For the mariners, liquorice was believed to be used as a nutritional substance. It is thought that the occupants of the North and
Baltic Sea, in Europe,

first came into contact with liquorice a long time ago. It is especially in these regions that people's fondness for liquorice has persisted, throughout many generations.

Thus you can explain the liquorice equator! In North Germany there are significantly more liquorice-fans than in the southern parts.