Lots of people wish to live in parts of the country where there are not many bedrooms. Therefore people are living in small bedrooms rather than large ones: that’s just what happens. If there’s a shortage of food then people eat smaller meals, if the pub runs out of beer then everyone drinks shorts. Shortages lead to smaller measures.
Government would not ban the consumption of gin if beer were to go short, government would not ban smaller plates if food were to be short, so quite why government thinks that the banning of small bedrooms is going to increase the supply of bedrooms is unknown to us.