Why do we think Dyson spheres exist. It's completely conjecture.
replies(8):
We are essentially searching for civilizations that have no other forms of energy (from a star) and have to rely on Dyson spheres for their energy.
We are excluding all those civilizations that have successfully used a combination of solar, wind, fission & fusion energy to drive their society.
I strongly believe that no matter what civilization, no matter how they look, what they consume or what they are made of, the core tenet of "human psychology", or more correctly "conscious being psychology" would evolve in the same way as is for us.
If, let us say, we solve our energy issues, and we have built ourselves a world that is sustainable. Would we think about building dyson spheres? No, because there is only so much you can do with energy. You need materials, ores, deposits, etc to actually build something new.
I guess the most advanced civilizations would harness the power of the stars, fusion, and build themselves sustainable habitats that can be floated into the eons.
It should also be considered a successful form of fusion energy capture, using the star as a gravity-contained reactor.
A Dyson sphere makes sense when your home planet is not enough by far, and even all the planets in your system are not enough.