Agreed. And there are enough former inmates in positions of authority to acknowledge that free-roaming Dementors are a danger to oneself. I can't imagine cold stone rooms in the North Sea, but I have seen them in the halls of the Wizengamot.
Don't forget that they've done nothing more for re-opening Diagon Alley and ensuring that there is traffic between Muggle and Magical London, thereby staunching one of our culture's richest sources of economy.