I think you're exaggerating how hard the retrofitting is to do. Office buildings tend to have tons of extra space for things like drop ceilings and utility chas

I think you're exaggerating how hard the retrofitting is to do. Office buildings tend to have tons of extra space for things like drop ceilings and utility chases that can be easily used to run plumbing and electrics. Natural lighting is a concern but these buildings also tend to have huge windows, that can light passively if the interior spaces that are being retrofitted in are designed correctly.