Really? When is this shown?
Blame
David Diaz
Jose Davis
the vast majority wouldnt and your probably underestimating the size of some strata
Christopher Bennett
Killy mentions moving between strata a few times
most characters understand that the city is layered so it's safe to assume they're not all cut off from each other
Caleb Watson
Where the fuck did they get all the shit to build a structure at least the size of the solar system? Is there enough materials/matter for that in our galaxy?
Wyatt Price
they have God machines that produce and harvest material infinitely from space and planets
Liam Carter
They extract matter from parallel universes. Think the Combine from Half Life
Alexander Taylor
The strata between human settlements are either crumbling, intraversable wasteland or has builder constantly building barriers so most human probably don't interact with other societies. Cibo's Tall People City are the exception since they mastered vehicles capable of flight and are shaped like blocks to better maneuver through strata. However they keeps calling Killy a kid upon meeting him because of his short height so it is possible they too have not seen other types of humans for a long time.
Asher Wood
a lot of blame! technology is basically magic, between the builders able to produce matter out of thin air, killy's handgun sized GBE able to generate nuclear fusion levels of energy, the level 9 safeguard able to casually teleport a chunk of the sun, the entire megastructure being as big and massive as it is yet not collapsing on itself
Mason Evans
Who knows, The whole mega structure is too complicated for me.
Matthew Brooks
wasn't there a crossover manga where killy and cibo showed up with a bunch of other characters carrying their original art styles?