I think it's something to do with the massive overcrowding that epitomised the slums in the early 20th C.
and that, after a certain age (I think - may be wrong) - 14 or something - girls particularly are legally entitled to their own room. I think this is to provide an area in which they can start generating more babies, in order to then get a house of their own.
( Je suis un vagabond is an unfunny, up your own arse middle class knob, Fri 28 May 2010, 15:23, Reply)