The setting up of a System Cron on a web server can be complex, and difficult for Administrators with limited experience, or maybe no admin access to the web server hosting phpBB.
A System Cron (set say to 5 or 15 minutes) is though pretty much essential to run extensions such as Digests effectively, and to ensure the Notification emails are delivered without delay.
Could an equivalent to the System Cron not simply be part of the standard phpBB feature set, e.g. a straightforward time that will wake up the phpBB at regular intervals ?
All the best