This was deliberate engineering to bring in fresh air. After the 1918 Flu, there was a desire for more fresh air inside homes. All of the apartments I lived in Chicago were built decades later, but the radiator layout persists.

Article[0] on it

  I’ve heard a story, and I don’t know if it’s an urban legend, that steam heat became popular after the 1918 flu pandemic because it was going to force overheating of units and make people open their windows and let the bad air out.

  I’ve never heard it put that way, but the flu pandemic had a huge impact on heating systems, because they actually changed the code requirements for heating systems when the pandemic was around, because they didn’t know what was causing this. They thought there was something in the air that was causing this. And so what they did is they started requiring buildings to be ventilated. Essentially, they changed the requirements for heating buildings so you had to maintain 70 degrees in the building with all the windows open in the sleeping rooms. So people see these great big huge radiators and think that that’s what they have to have in the house. Usually, the reason those radiators are so big is because they had to heat the house with windows open.

Edit: switched out to different article focused on Chicago