It's all about incentives. A huge percentage of the human population has decided to live in cities because they offer a variety of incentives to live there. The

It's all about incentives. A huge percentage of the human population has decided to live in cities because they offer a variety of incentives to live there. The transformation isn't complete but if the benefits were even greater then you could eventually see a complete shift. Who knows what incentives a hyper-advanced civilization might have? Maybe life in space is a million times more appealing than life on a planet for a sufficiently advanced technology level. If estimates are to be believed then the resource wealth of the solar system far exceeds anything contained within the Earth. If you've solved the problems of efficient space propulsion, resource extraction and construction then you would have access to an abundance of everything you need. Space also has a lot more space, enough room for any person or group of people to build whatever they want without annoying their neighbours. It also has more energy both in the form of sunlight and radioactive elements. So yes, maybe energy and matter are nearly free for a true space faring civilization and maybe that's the reason no one would want to stay behind or at least so few that they would leave very little evidence of their presence.