This is not even a little bit true. What you're implying is that businesses are required by law to keep all internal communications in case someday there's litigation, and that is just flatly false.

Deleting data once litigation has been initiated is tampering/obstruction. Deleting data when not under litigation is the company's choice, with very few exceptions. Many companies explicitly require all communication be ephemeral - email, messaging, etc. it explicitly only preserved for X days and then deleted entirely from all systems.