The reminders system is scheduled to be updated in the near future as there are some shortcomings. First, a quick background...
Back in 2006, the suggested setup for email notifications was that the site Administrator would create team "email aliases" which would forward to all the members of the team. These aliases were really useful because if the name of the alias was something like "email@example.com" then anyone on that team could quickly communicate to each other.
With the assumption that team email aliases existed, there was (and still is) a setting for each team called the "schedule change email address" which stored a single email address (the team email alias) and by using that all members of the team would automatically receive email notifications of changes without having to subscribe individually.
Given that assumption the reminders feature was added in 2008 and piggy-backed on the idea that team email aliases both existed and were being used as the team schedule change email. So then it was just a matter of enabling the reminders for that team.
This approach still works, and to set it up here's how:
1) Create the team email alias in System Administration -> Email Administration -> Aliases.
2) Set the team "send schedule changes to" email address in System Administration -> Season Defaults -> (select season) -> Scheduling.
3) Enable reminders for the team in System Administration -> Season Defaults -> (select season) -> Reminders. The options are whether or not they're enabled for a team, and if so, how many days in advance to start sending the reminders. The default is 2 days - which means that for the morning of AND the day before AND two days before something happens (game / practice / event) for that team, send a reminder email. There is one email generated and if there are multiple things happening in the given date range, it will include all those things.
This implementation has limitations. First, some of the larger associations have taken the stance that creating team aliases for all their teams (on their behalf) is too work-intensive of a task - and therefore the team aliases never get created in the first place. Second, email notification (and particularly reminders) tends to be an individual preference rather than a team-wide one.
In addition, when the ability to subscribe to calendar feeds was added there was less of a need for email reminders since the native calendar app on the phone (or in Outlook) would show the days upcoming appointments as long as you had that app / program open. Plus in 2015 those feeds also added the ability to do reminders.
In any case, the plans are that the reminders feature will be re-implemented in the future in a similar way to how the email subscriptions are setup where an individual can choose to enable email reminders (or text message reminders) on their own. We do not have an ETA for this currently given that there are suitable workarounds available.