There is something in what you say,when you high-lighted you moved out,but others chose too stay,and that is the 'issue' S/Housing or call it what you want even dare i say it Council Housing is not for life.
Surely the problem there is lets say its 100K to build a house but do to The Right To Buy scheme the H/A has to sell at a discount of that cost figure,there's no return for the H/A and therefore they won't build surely ?