Is it not the case that the developers want to build 4/5 beds where possible to maximize profit, the planners want 3/4 beds for families and the majority don't want to downsize but want to stay in the house that they have put so much into? So who wants a smaller 1/2 bed house? Only those willing to downsize and childless couples. That's not a big cohort of people.The lack of a suitable mix of housing in many areas is a huge disincentive for many older people to downsize as it often means they would have to leave the area and move away.
The planning process which encouraged or indeed only allowed a standard type of house to be built is at fault.
Many, many plans to add a mix of smaller houses and apartments into an area of standard 3- or 4- bedroom houses was met with dismay and stonewalled by the very people who now moan about the lack of suitable housing to move into.
The planners and politicians who are responsible for this state of affairs are only interested in the short term - ie can I get re-elected next year or the year after - long term housing planning is non-existent in this country
Not being sentimental or good at DIY the idea of a small energy efficient 2 bed sounds great to me. Long way off though.