You do to vote or you can show your voter ID card. It varies by state. The problem is illegal immigrants. Let's just kick them out. I'm not nearly as concerned with the inner city blacks being bussed around from town to town. That's a relatively minor problem and only effects urban areas that lean democrat anyway. Not so much the presedintial elections.
Too much potential for abuse by the government. I don't like the SSN system as it is
All that being said, there are tons of good arguments for it here by everyone so maybe I could come around.
It would have to be free, and it would have to be legal to not have one
We are putting some carts before some horses. There are things states could right now that would greatly reduce issues. Crosscheck. The federal government has a registry of every resident alien here in the country and also everyone with a federal felony conviction. Some states already cross reference their voter rolls against those databases. Not every state does this because GCF's party screams bloody murder.