Do you have permission?

Something is bothering me.

On a forum I'm a member of, there is periodically a question about travelling abroad alone with your child/ren, particularly to the US.

The question revolves around what authorisation you have to take your child out of the country (or into another one) without both parents being present.

A lot of families have obtained a notarised authorisation stating that the father of the child gives the mother (or vice versa) permission to travel alone with the child.

Got me thinking. Why the hell should you have to prove that you have the right to travel with your child? Why is there an assumption that a child is in a 2 parent family anyway? If I was a single parent, would I need to have the father's permission to enter, e.g. the US with my child? And what makes some passport control officers choose certain individuals to question? I know of several people who have been asked for authorisation several times and many others who have never been asked.

Most people would say that if there's a possibility that you will be refused entry to the country then you might as well get the notarised permission. But for me, it is about the principle of the thing.

I understand that in a few cases, one parent may be trying to remove the child from the care of the other parent illegally. But surely, that happens so rarely that isn't the onus on the authorities to prove these few illegal cases, rather than on parents to prove that they are legal and above board?
Oh, no, silly me, its just the gloomongerers and pessimists who get to make the rules, common sense and TRUST doesn't come into it.
Makes me sad.