This isn't accurate. There are certainly companies that have extremely in-depth Data Loss Prevention toolsets and teams - everything anyone downloads or moves is logged and alerts fire if things look out of the ordinary. Google clearly had tons of data about how Anthony Levandowski was able to exfiltrate lots of info when he left.

The issue that building these systems accurately so they are NOT a constant annoyance is difficult, expensive, and takes a large team to support well.