our company moved away from slack distinctly because it was too cumbersome for them to look into a person's chat logs. IIRC they also notify the user when a manager requested/looked at their logs. They moved to a local instance of Mattermost for 'privacy' reasons, but it was the opposite of what you would think. The privacy isn't of the user, but rather they wanted a lack of privacy.

Yes. Also, just think about the amount of proprietary / business sensitive info people are sharing on slack... even though they KNOW slack is a 3rd party