Offices & Flats to Let!

Over the last nine or ten years all around the area that I live has been re-developed on a very large scale and it is a long way from being finished. There has also been large scale re-development in other parts of the city but what I cannot understand is why?
Most of the offices remain empty and many have been for the last several years since they were completed so it can't be anything to do with the recession. As for the apartments and flats, this city can only support a limited amount of yuppies and students are not in the market for buying penthouse pigeon holes.
I really think the planning committees should do a survey of empty offices and homes throughout every city and town before allowing permission for huge quantities of offices and flats to be built only to remain empty for years. This may keep construction workers in paid employment but it is a waste of resources especially when the end result remains empty.
There are any amount of people who have nowhere decent to live as well as those who cannot afford to buy in the places where their families have lived and worked for generations, in country areas and seaside towns. Then there are the loaded gentry who buy the best properties in all the beauty spots around the country for 'holiday homes'. As far as I'm concerned this is obscene greed because we can only live in one place at a time and then they have the gall to complain if any of their properties is taken over by squatters. This is not an action which I condone, let's just call it 'poetic justice'!
If every empty office across the country was turned into flats, then if all the empty flats and houses were occupied and if people were taxed so high on any property other than the one used as their main home, there would be no need to build the twenty thousand or so homes we are told will be needed in the next twenty years. This will also preserve the greenfield sites and all the brownfield sites could be turned into parks!
Problem solved! What a lovely thought!!