It's just not their forte. They move paper (and highly profitable paper spam!) around the world using lots of people in a system they control end to end. Email

It's just not their forte. They move paper (and highly profitable paper spam!) around the world using lots of people in a system they control end to end. Email has none of these properties. Maybe 200 people, tops, run Gmail. Spam is a liability, not a profit center. No one controls the Internet. Etc. This is like asking why Amtrak doesn't take over the mobile phone business.