I'm not voting today, but that's simply because I didn't change my registration when I moved.
That's no excuse!
Right in front of me in line was a man who was illiterate, spoke no English, and was not registered. He said he had just moved to Maryland from DC. The election officials were very understanding. They gave him a provisional ballot, had somebody read to him in Spanish, and he got to vote.
You have to realize that the whole point is to encourage people to vote and to make them feel good about it. You can't do that if you turn voters away. A would-be voter getting turned away would be like a company picnic where your kid goes home crying because he doesn't get his face painted. The folks in charge will do anything to avoid having that happen.