Why were the streets of European cities narrow and high-rise buildings?

In the Middle Ages, political and cultural centers in the form of cities began to form in Europe. The urbanization of the population gradually proceeded. But after several centuries, the urban population has grown significantly. In order to accommodate all residents in small spaces, high multi-storey buildings were erected, and the streets became closer and closer. This method was used in order to accommodate as many people as possible in the city, who served as labor force in factories and factories.