Meetings require more coordination since only one person can speak at a time and there are fewer non-verbal cues to communicate which topics are resonating with you. You also can't continue smaller conversations with people after a meeting. Everything is more formalized.
Likewise, conversations outside of meetings go on in Slack, generally. You could set up a zoom meeting with someone informally, but it feels too "heavy" an operation compared to a in-person hallway chat.
In person, I feel like people are more likely to be critical of their work, workplace, bosses, and coworkers. Now I don't think people should go overboard and whine all the time, but I think it's valuable to get stuff off your chest once in a while, and doing that in person, to me, feels natural, and it's not "recorded" anywhere (Slack messages aren't deleted and a lot of our meetings are recorded for others to view later).
Anyway, what I'm getting at is the channels for communication are more "formalized" and it has a sort of chilling effect on our expressiveness in conversations about our work's office culture.