Because this is not forcing?
I'm not _forcing_ you give me $100, not at all. It's just that if you _choose_ not to give me $100 I will continue to stand in your way and prevent you front getting inside.
An obligation that is not enforced is not an obligation. A decision that only stays voluntarily as long as everybody complies was never voluntarily in the first place.
I'm usually a very phlegmatic, law-abiding citizen but man, where does this love for newspeak and doublethink come from, all of the sudden?