At least some of them do. This one from Nebraska says:
The affidavit shall be sworn or affirmed before a notary public and shall contain statements substantially as follows: I was born a citizen of the United States of America and was subject exclusively to the jurisdiction of the United States of America, owing allegiance to no other country at the time of my birth. On the day I was born, both my birth mother and birth father were citizens of the United States of America.
That bill just tries to come up with some language to exclude Barack Obama based on the facts of his birth. There is nothing in the Constitution about parents.
Perhaps the birthers want to the force the issue so that the courts will decide who’s eligible to be president. Bad move because they will lose.