There are two reasons a civilisation reaches for another world, and they lead to entirely different destinations.
The first reason is flight. This world is becoming difficult, so let us secure another. It is the oldest human motive dressed in titanium, and it is worth naming plainly because it is doing a great deal of quiet work in the current conversation about space.
The second reason is the expansion of understanding — the sense, ancient in every tradition that has looked at the sky, that a mind which knows only one world does not yet know what a world is. This is closer to what Sanskrit calls jijñāsā: the desire to know, held as a discipline rather than a hunger.
The distinction matters because motive determines conduct, and conduct at that distance cannot be corrected from here. A settlement founded as an escape will reproduce the conditions it escaped, because it carries the unexamined appetite that produced them. A settlement founded as an act of understanding has at least the possibility of being something new.