FWIW this is also very true in the United States, layouts of new units are generally completely unsuitable for families and that's why upper middle class but not rich enough folks in San Francisco tend to rent/buy condos in older buildings.
Different problem than in France I guess, where the square meterage is just too low, here in the US it's just wasted.
US flats generally have a lot more due to different social standards; the in-unit washer/dryer is not common globally, for example. Or apartments with double vanity bathrooms.
The families thing is also because all other things being equal, more bedrooms will lower the price per sq ft of a unit due to weaker demand; and right now studio and one-bedroom demand is so high that you could reasonably build a building full of them and generate profits.
FWIW this is also very true in the United States, layouts of new units are generally completely unsuitable for families and that's why upper middle class but not rich enough folks in San Francisco tend to rent/buy condos in older buildings.
Different problem than in France I guess, where the square meterage is just too low, here in the US it's just wasted.