Or was retrofitting older buildings with new amenities like indoor plumbing/central heating/electricity often too expensive to be worthwhile?
Most of the focus on urban development at this time is about new forms of transit allowing cities to grow during a period of rapid urbanization, but there tends to be less focus at the micro level as to why someone would redevelop a specific plot of land.
Edit: for clarification I mean late 1800's early 1900's
In the 1880's the French government resolved that there should be a train station within 20 minutes of every village, and worldwide, the transport of stone and machinery and manpower was moving byrailroad, where previously it had been horse and boat, and the entire facade and fresques of building could come from coal powered stone quarry 75 miles away.
The mechanization also reached into stone masonry and mass production of cranes, scaffolds and building machinery and concrete.
Steel became very cheap, and more advanced, and in Chicago the first steel frame buildings were built in the 1880s, when brick and mortar had reached it's maximum height of 16 stories high. Steel bridges became the standard after stone bridges.
The printing industry was very efficient, and good illustrated works depicting building ornamentation and architecture were sold worldwide to all the construction companies and artists, so that great artists could publish and copy studies of ornamental stone and iron work. The worldwide art scene was very vibrant: Art deco, art nouveau, belle epoque raging through every decade. After the 1930's, buildings started to transcend ancient laws of architectural beauty and grace and experiment with stalinesque and matter-of-fact architecture which mutated into prefabricated cheap city center buildings of the 1950's and 60's.