Just the functioning of Indonesian law. If you lived there you would find yourself needing to declare your religious affiliation constantly, plus, you'd find it necessary to dclare the religious affiliation of your children according to that of their father, step-father, or other male head of household.
It's a foreign country with foreign ways, many of them totally incomprehensible to Americans.
I think this is done simply for the father as well who wouldn't want to be ostracized for having non-muslim children.
But, we all know anyway that Barry is a Farrakhan black extremist with terrorist associations.
Had this been a Republican, he'd never survived the press out of even Iowa.