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

It stops drafts from the window before they reach occupants. Yes, it is less efficient in terms of total heat inside the structure, but its more effective at avoiding uncomfortably cold spots, which is (in most places at most times of year) more important, plus, the utility lost to the occupied under-window space is less than the utility that would be lost for the same space elsewhere; the window already limiting alternate uses.

Offices that use air handlers and VAVs also have narrow VAV zones along all perimeter windows. It’s for comfort, windows are where the most heat is lost/gained so heating or cooling those zones makes the space more comfortable for the people inside those areas.

When the cold air coming from the window drops, it pushes the rising hot air out into the room. Overall loss of heat, but feels better for the human occupants long term.

No furniture in front of the window.

I think a lot of those old central heat systems you couldn't actually control the heat, being able to lose a lot of heat to the window if you wanted was probably a feature. I was watching a video on old soviet blocks in cold areas and it sounded like it really sucked to live too close to the central heater and have to deal with super hot houses