In a corporate env, you want to be able to attach/display extra information about a user:
e.g Phone Number, Geographical Location, etc.
At the simplest level, they are what we (and I guess most corp users) would need.
However, to cater for different requirements, maybe you want to be able to add custom properties to a user.
You may want to mark whether these fields are required or optional
These fields must appear on the "Add New User" form.
You need to be able to map these fields to external user management.