Re: @AC It's not "why", it's "how"
The larger issue... is automatic voter registration. You get a drivers license, you're eligible and registered to vote. It sounds good, but when you allow illegal aliens or even green card holders to get a drivers license, they are then being registered to vote. (The devil is in the details.)
Err... no. I got an American driver's license in 1984. At the time I did NOT have a green card. I was not registered to vote, no doubt because the people at the license place knew damn well that I was not eligible as I waved my Irish diver's license and passport at them when I got the license. Even when I got the green card and went to renew the license, I was not automatically registered to vote. I was not registered to vote until after I got US citizenship... and I had to join a line to do that. It was NOT automatic.
The rules have changed since I got my license; I was a 'student' and was in the process of getting a master's degree at a fine American university in north west Indiana. An obscure place with a French name and perhaps 10,000 undergrads, you probably may never have heard of it. It is now much, much, MUCH harder to get an American driver's license. Thank you so much, Mohamed Atta.