Use Active Directory Instead of Employee Database

Have a question for the experts.  In many corporations, is Active Directory regularly used instead of an employee database to obtain info such as employee #, hire date, extension ... on employees?

I'm being asked to do use this instead of pulling the info from the employee db.  Many web pages look for this info to work.  

It would mean creating custom fields in AD.  And it doesn't seem like a proper place for them.  But maybe this is how it is done now.

Whatcha think?
JS