Quoting from the concept page Preferences and User profile:
- Avoid polluting User, MgnlUser APIs with non-security-related concerns
- Enable external users to set magnolia and/or admincentral preferences
- Provide it as a backbone for public user profiles (via PUR)
- Allow developers and templaters to consume user info
—linked support ticket reports that external (LDAP) users are pretty out-of-luck with our current user properties setup; for instance, they cannot benefit from the time-zone preference.