I think in a RPG, like in any story worth telling, the characters have friends, enemies, siblings, sometimes parents or children, workmates, sometimes a love interest/ fiancee/ spouse. And all these do flesh out the characters, allowing the reader to see different aspects of their personalities.
Even the one who saves the world (depending on setting), can't do it alone, he still needs friends and workmates in order to accomplish it. (And enemies to attempt to hinder his endeavour).
But how can one build meaningful relationships when a budding relationship of any kind, which promises to develop, is halted by a writer disappearing?
Don't you need relationships in order to build a three-dimensional story? Is it really necessary to get only to have relationships with NPCs that you can write for or with other characters of yours, just to ensure the needed continuity?
It feels pitiful that a certain character has no friends aboard his own ship, except a NPC I can write for. (Hopefully he'll get another friend soon, if it goes according to our plan, and hopefully it will last...) He had a friend aboard an allied ship... but the writer vanished, and said character is up for adoption for 2 months, nobody wanting him yet. (And yes, he is more than my character's friend and another writer's character's love interest). Now hopefully he gets another friend instead of that one.
And this is valid for other characters too. In some cases, including vanishing siblings or love interests/ fiances/ spouses. As if one could start anew every few months... as if it made sense not to have any kind of stable, long-lasting relationships around.
Do you have a sibling or a son for spare? Yes, I know this question would sound crazy... but leaving a family relationship without one of the members looks identically so.