There is a new type of I.D ("REAL ID" in WI) that allows access to certain areas that a regular photo I.D. or Driver's License does't.
When you renew your license there are extra things you need to provide in order to get it. If you choose not to, the extra items are not required.
Maybe it's something like that.
From the WI DOT website -
http://wisconsindot.gov/Pages/dmv/li...ly/realid.aspx