It's hard to transform many office buildings into residential spaces, unless you demolish them and rebuild.
Office buildings usually have huge floorplans while residential places require windows, so any space within ~5-6meters from the wall is basically useless (bathrooms, elevator shafts, storage spacce, stairways and not much else can be positioned there)
The New York Times had a nice interactive article recently for subscribers showing how some office buildings can be and have been converted to residential. Most of the illustrations that tell the story didn’t seem to get captured by the Wayback Machine, unfortunately:
Office buildings usually have huge floorplans while residential places require windows, so any space within ~5-6meters from the wall is basically useless (bathrooms, elevator shafts, storage spacce, stairways and not much else can be positioned there)