We use isolation transformers for many reasons, one of them is may be safety. So why not just keep the distribution transformers floating? If they're floating, then someone touches the live wire, I don't see how this would present a safety hazard.
The closest earthing system to this configuration is "IT". But I don't want to keep the impedance in the leaking current path, we'll keep it as high as possible, floating.
Also,it does not look like we're still using the earth as a conductor for economic reasons since the neutral wire is pretty much always provided.
What am I missing here?