Many coworkers, vtubers included, will just stay as such and never contact outside the job. But it's also very easy to form a connection when you have someone dealing with the same workplace nonsense as you.
This is even more amplified as a vtuber because vtubing is inherently a social job. All vtubers, hell all streamers, form some sort of connection with their chat. That's literally the point of streaming. Then corpo vtubers will debut with genmates, will have senpai/kouhai around and they'll get to know each other, usually before debut and certainly after. They do collabs, come up with ideas, spend late nights chatting, etc. They're also a shoulder to cry on and vent to about their issues, because the person they're talking to is likely going through the same shit and can understand.
While doing all of that is part of the job, it also just naturally results in becoming closer and forming a bond. And when most vtubers are introverted, anti-social weirdos, they would want to keep that connection. Aqua's entire character arc over 6 years was about this and now she has so many friends she wouldn't have had otherwise. Of course, that connection can last even after someone leaves the workplace (we're getting frequent stories about Aqua hanging out with Holos) but it still fucking sucks because the job is what got them together in the first place. And with vtubing, that also means no more onscreen interaction, which feels bad for both the chuuba and the fans.