“…and what looks like normalized civilian arms is just the fact that these stories and adventures are narrowly focused on very exceptional people in very exceptional circumstances.”

This, I think. Even in Star Trek, the shows and films are generally all set on the frontier — one that borders with hostile governments or unknown threats. And even when we are in civilized space, we’re dealing with internal threats like the Maquis. I believe we have seen ships with little or no armament — I’m thinking of Beverly’s medical ship in “All Good Things” or even various civilian ships in TOS.

And I think we’ve explained Solo above: “It is a period of civil war” is the first thing we see in the first film. Not only is Han a criminal, he’s not aligned with either side of the fight — he’s a target for pretty much everybody.