Personally, I think this requirement for secondary information is not only a harassement of gun purchasers but patently illegal.
One is required by DMV to submit a change of address form within 10 days of moving to a new location. The DMV issued state-id/DL card is required to obtain state medicaid, welfare and other benefits. It is also used by LEOs as an official form of ID. TSA and the FAA require you to present a state issued ID card before flying.
However, in order to exercise your rights you are asked to provide another proof of residency, such as a utility bill -- a document not issued by a government agency. Some persons, such as yourself, may not be able to provide such documents. Consider a young, single mother living with friends or her boyfriend -- the utilities are in his name, she doesn't own a car, have a rental/lease agreement in her name and may even have a PO Box for her bills due to her living situation. The state will not permit her to purchase a firearm, thus denying her rights under the 2nd Amendment.
It's yet another "gun control" scheme to keep guns out of the hands of the poor and to harrass those intending to legally purchase a firearm.