NIMBY is real problem also. People like the idea of greater housing stock and lower prices but God forbid you build a real estate around the beautiful countryside that MUST be preserved! If houses get built I might have to associate with the chavs so build it somewhere or else I will vote my local MP out! It is this attitude that leads to a horrendously complex planning code that stifles development.

The other major factor in houses not being built is no one wants to develop cheap accommodation. Everyone wants to build luxury apartments because the profit margins are larger. That is why proper social housing has only been the domain of governments as their primary concern has not been about profit maximization. Issue is most governments don't have the appetite for this and even if they did, they are too broke to build houses at scale. Due to this the problems get worse as housing stock does not match population growth. This is especially the case in the big cities where the jobs are.