Is that a French thing - IP rights that can't be given up?
Moral rights to me are embodied in the right to be named as author of your works. And I can't see why you'd want to allow that to be taken away, eg in a contract of work, against the authors wishes. Where's the benefit in stimulating creative expression or for the public domain?
Generally USA has rights that can't be given up; though you can chose not to exercise some of them. For example you can't sell yourself in to slavery AFAICT (or at least it wouldn't be lawful to be bought which in practical terms is equivalent).
You can have that right if you negotiate for it in a contract or make it a condition of the license you release the work under.
The more interesting question is why other countries want there to be rights granted by law that authors cannot give up.