There are other benefits. It's a federal crime to tamper with US Postal mail or private mailboxes. It's also a federal crime to commit fraud by using the USPS

There are other benefits. It's a federal crime to tamper with US Postal mail or private mailboxes. It's also a federal crime to commit fraud by using the USPS. It's somewhat like fax, there are differential legal protections in place that make it a preferred service for certain scenarios.