apart from political and social agendas, it also has a very real reason: a difference between housing and office buldings is the plumbing. Office buldings usually have too few access points for water in order to turn it into adequate kitchen and bath units. A refit would be almost as expensive as buiding a new building. Therfore its uneconomic to do so, unless you build really big appartments, which noone could pay the rent for except some millionaires. And those do rent what they want anyways, so... nope.