During the 1800s there were four sets of building regulations (or rather, laws) for Christiania (the name of Oslo back then), which regulated everything from the width of the streets to how many floors buildings could be. In 1827 the minimum street width became 11.35m, then 12.60 in 1842, 15.75 in 1875 and 20m in 1899. (https://no.wikipedia.org/wiki/Murbyen_(Oslo) has a good overview).
The background for the regulation was the switch from unregulated wood buildings to requiring mainly brick as building material - there were some major fires before using bricks became the law.
I live just around the corner from one of the photos - the building in that photo hasn't changed much since back then.
The actual noise levels may have been higher. Regardless, I think the main reason is ventilation. With coal and wood heating streets were designed to act as valleys pushing air through. Also, I hard that old European cities were built with airflow in mind. Whole streets were uninterrupted with trees while some have them.
Also I heard an opinion that Wrocław is one of the most polluted cities because it got a lot of new buildings that break the airflow on main streets.
Delivery wagons might be drawn with a team of two or even four horses (or even bullocks). You'd want to be able to turn them around in such streets. Certainly that was the case for Australian country town main streets laid down in the 1800s
