I think the simple answer is that, within the UK at least, your employer did not authorise it for anything other than official use. Similarly that the government did not have it on the list of admissable documents for official proof of ID or age. I have three forms of official ID. All of them, like yours, supported by various official checks, but each only valid for what they were issued for, i.e. access to the establishements owned by the issuing authority, so I always carry my plastic driving license.
In your case I believe all is about to change for reasons you have stated.
Means of Identification (Licensing): 14 Mar 2011: House of Commons debates (TheyWorkForYou.com)