It seems that people have interest in writing only certain characters, or only certain aspects of the characters' lives, while a story implies writing several character types in several circumstances which make sense for their lives.
E.g. a Navy officer has in the story not only the role to charm ladies at a party, but mainly to take part in battles or to lead work scenes as well... to show only a few aspects. He should interact also with his superiors, with allied officers, he can lead an exploring team, enforce the law under his competence, etc. And among the Navy officers, if they were chosen for example, there can be (and should be) a diversity of personalities as well: the ambitious perfectionist, the drunkard/ gambler who can be blackmailed or can blackmail others into betrayal or extorsion, the womanizer (or soft lover, because he can be sincere too) who spills a secret to his lover by mistake, the one wh o isn't professionally good but he has the right upbringing and patronnage and power thirst in order to advance stepping on corpses....
So if the story needs these aspects/ scenes/ characters and nobody else is willing to write them... somebody has to. We are all here, first and foremost, to write an interesting story together, immersing ourselves in the right setting through this. it seems I will always be this 'someone', because I could never say/ think 'I have no interest in writing this character/ scene.' if it is a part of the story i love and it makes sense in our setting, then I should clearly do all research and everything possible to make the story happen.
...And this is how some people get with more temporary characters than others, and with writing for more NPCs than others who don't have interest in them or who see them less of a character because they have less writing time. They aren't less.
There had been a while when I was regretting everything others didn't do, just because I was convinced that, since i am writing with others, everything should be shared. Now I don't care anymore about this, neither about other people's rants that people shouldn't have so many characters or NPCs. They are there because they are needed in the story and nobody else was willing to write them. That's all, folks. Somebody has to do it in order to have a well-rounded story, a well-rounded portrayal of the world we are writing about.