There is also the aspect of being on the record in corporate chat. There is way more on the line when everything is recorded than informal in person talking. People also 'have to be there' with their jobs, doing something they necessarily do not enjoy. On IRC in the 90s when everyone was anonymous and nothing was on the line, you had the social freedom to be more open, and the people who wanted to be there didn't have to be paid to be there.
Yet another good reason why corporate chat message TTLs should be no more than 7-14 days.
(Another is that the default of "forever" in things like Slack and Mattermost means that a compromise of a single user account gets to see every DM (including sensitive stuff DMed like passwords or PII) ever sent or received by that user. It's insane. It's also able to be subpoenaed. Expire your messages!)
People get really annoyed that they cannot find answers to previous questions, and if you have q&a website to get around that, your just moving the chat goalposts around. Not to mention its a higher friction process, so people go ask questions anyway on the company slack.
Also screenshots are a thing and easy to do in secret impulsively, recording stuff when your talking in person has a much higher threshold, and far less people are typically listening.
Also once you get to a certain size, there are legislative retention requirements and legal holds.
