Riginslinger, Rig, if those are the documents you have to show in AZ to apply for public benefits, what document(s) do you need to prove you're a legal US resident?

Also, someone living in Arizona could be applying for Social Security or Medicare or Veterans' benefits - federal programs - and wouldn't have to have their main residence in AZ to qualify.
Plus, most states don't require you to change your DL from your former state to the new one for 3 to 6 months after you move there. So someone who's recently moved to Arizona might well be eligible for some state benefits yet still have, say, a California DL.