I personally saw the advice to cc a lawyer with a legal question in order to bring a conversation under attorney client privilege.
The penalty they’re facing in now way accounts for the money they saved by concealing evidence, which basically means “keep doing it, it works!”
One can see how regular folks might consider the practice of automatically destroying chat and email messages after one to three months destruction of material which could be evidence.
"Never erase anything" seems to work fine for highly-regulated businesses like banks. And while long-term storage of electronic communications isn't free of charge, it's not at all in the same ballpark as storing decades of paper memos and other paper internal office communications.
Also: The widespread directive to "magically" turn documents into privileged communication with lawyers makes Google's bad intent very, very clear.
On the other hand, humans do not like being watched and documented constantly - I think it is a burden to society's mental well-being.
I would not want to be constantly recorded in my team staff meetings, in office or in zoom.
I doubt it, expiring chats are widespread even among consumers.