That is correct. They don't vote, along with 50% of the rest of the population that should in this case.
I don't think people SHOULD vote under these circumstances:
1. They literally don't care who wins.
2. They can't be bothered to get an acceptable ID to prove they are eligible to vote.
3. They can't be bothered to put down the XBOX controller, get out of Mom and Dad's basement and go vote.
4. They have no clue what issues are facing the country and what the candidates are likely to do about them.