I have wondered about this too, but I guess it isn't too hard to see what a time consuming task it would be to constantly update a full manual with so much changing every month. I guess the slight inconvenience is the price paid for the success of rolling updates.
I use the ezine to discover new features, but the online documentation is also excellent for a quick lookup and always seems to be up to date. As an example a search for 'Cakewalk load balancing,' one of this months new features, yields this excellent guide as the first organic result:
https://www.cakewalk.com/Documentation?product=SONAR&language=3&help=NewFeatures.002.html Many software developers don't write manuals anymore (Melodyne springs to mind with not even an online written guide), though this is not a position I could ever defend. A bunch of videos does not a manual make! I loves me a good read of the user guide:) That said, we readers seem to be an increasingly endangered species.