How do you figure humanity spreads if it never leaves those safe spaces?
Also where does it say that humanity have to spread? I’m sympathetic with people whose current location become undesirable and they have to move to a new place. But “spreading” is not the goal.
Society uses, builds, and works to maintain delusions like this because it helps keep us all from a mad max future. It’s one of those ‘useful to believe’ things most of the time.
But don’t buy it so much you let someone use it against you as a weapon, instead of as a mutual agreement.