Housing crisis

If the UK could cope with rebuilding over 2 million destroyed homes after WW2 and probably the same number severely damaged - how come housing targets of 200,000 new properties a year are unmet these days ?

http://www.bbc.co.uk/schoolradio/subjects/history/ww2clips/children/bombed_out

More than 2,000,000 homes were destroyed in Britain by enemy bombs - about 60% of them in London. A great many more were severely damaged.