I think our willingness to be vulnerable, and generally to invest in a friendship, increases as we spend more time with people.
Two places where this doesn't hold, for me, are at work and at church, and they differ in opposing directions: I spend the most time with coworkers, but conflicts of interest and power dynamics discourage closeness; whereas church encourages honesty and vulnerability even with people we don't really know. Despite working for a year (and attending church my whole life), I haven't quite figured out how to fit these into my understanding of relationships.
At work, I generally feel disconnected from the personal lives of my coworkers. Conversation revolves around the job and safe topics like sports, shows, or books. I think this is normal (?), but there are also people who push for diversity and inclusion initiatives and advocate their political stances, which kind of tears down the corporate abstraction and requires engaging with our shared humanity. I've participated a little, in donation drives and discussion groups, but also have kind of refrained--mostly because I associate that kind of engagement with church or my personal life, and because work feels most comfortable for me as semi-anonymous, technical... work. But it also makes sense to me to discuss these ideas in the workplace because of how much influence and wealth companies have as a whole. Not sure what a good balance between robotic code monkey and full-dimensional authenticity would look like.
As for church, I don't mind transparency, but it's not clear to me if transparency is helpful without also investing additional time in people--and time, of course, is always in short supply. I recall feeling this way about FICCC Bible studies: if there's no meaningful interaction with the middle-aged local community members outside of the Bible study itself, then sharing feels more like a formality.
Maybe there's some element of catharsis in sharing something painful with a group, but if there's nobody to walk alongside you afterward, then it feels... kind of bad. And equally so as the listener who isn't sure what to do about it, isn't very close, is too busy, or any other number of reasons. So I guess it's usually easier to just keep things to ourselves.