This varies immensely per organisation so it's always kind of dangerous to generalise like this. For example: The use-case you quote does not align with my experience of (bigcorp) chats at all.
I think either you misunderstood the scope of what I meant ("I need to see what I just wrote") or I misunderstood the scope of what you meant ("I need to see what I wrote last month") when talking about logging. I should have asked for a more specific definition.
Chats in organizations are specifically for when email is not realtime enough but it's important to keep a record of the conversations for some time.