As an aside, Aurora is in the fourteen-ish bracket and is pretty much adopted by the crew as a whole, who are as maternal and caring as you'd expect from a bunch of breed machines. Shekka was earmarked to have a few lines about her on the subject but that kinda slipped out the wayside/there wasn't a good spot for it, so instead you get her buying a junk part for Aurora. I'm sure you can link implications.
Consider CoC, it's a bit more obvious there given the nature of its world building and lack there of; Dominika is that oral-fiend wizard in Tel'andre. Now, looking up on the wiki to actually remember her name, it turns out she interacts with another character, but otherwise she has this backstory, these goals, brings more setting into light for the city that only comes up for Dominika. If she were removed, beyond a little setting information that affects no one else there'd be no change on the game. She's in a bubble. A bubble that has "destroy the plane to escape, maybe" on it, which makes it especially egregious.
Now, of course, CoC has a lot of orphaned characters and she was one of them, but an example all the same. Consider others; we have Urta who mentions hermaphrodites being shunned by the city (PC never is, problem invented just for herself and I don't think even comes up for Katherine, either, come to think of it) and even has her own quest and deity sitting in her balls. Still could be removed and the only thing that effects if Edyrn, in passing. She's in a bubble and probably a closer example given the "just-effecting her problem."
Now, of course, TiTs still has a few of those problems. Some of that is avoided by way of planets being a thing as opposed to nondescript apocolyptic destinations, giving everyone culture and identity etc to link them up, they share exposition. All of Savin's chararcters are largely connected somehow, even when it's a little painful. (Looking at you, pirate boss and Kaede.) The earlier you are in the game and the more writers there are in a particular venue the more it'll happen, of course, but it's still something that we want to avoid. In the perfect world characters would interact with each other, too, of course. That's a lot of effort and potential author collaboration, tho.
It's assumed, obv.