There are several legal digital formats (e.g. PSK31, FT8, RTTY) that, while not encrypted, will render 'reading the mail' hard for anyone not aware of those for

There are several legal digital formats (e.g. PSK31, FT8, RTTY) that, while not encrypted, will render 'reading the mail' hard for anyone not aware of those formats and/or the right equipment and where to get it. Most hams can enjoy the hobby without encryption. The limits discourage uses that endanger the hobby.