Users (not administrators) need notifications in 2 circumstances
When they are at or over credits using AGOL tools. The need for this increases as more web-based tools that consume credits are developed and released.
When they have been given rights, or when rights are revoked, to a licensed product. For example, if an administrator provides access to GeoPlanner - the user should get an email confirming they now have access - as opposed to having to look in their AGOL profile. They should also get an email if and when access to that license is revoked.