It reflects the interests of special interest copyright groups who work both to get these treaties written with terms favorable to themselves, and to get laws passed to enforce them.

When those laws are passed they try to get the laws to be stronger than the treaty. Thereby leading to differences in laws and a push for a new treaty to "harmonize" different copyright regimes. Strangely, the new treaty harmonizes on the strong end of the laws passed, thereby creating a ratchet effect.

After decades of success on things like copyright terms, Disney finally reached the end of the road when the Trans-Pacific Partnership Agreement died. As a result Steamboat Willie, written in 1924, will become public domain in 2024, some 68 years after it was originally supposed to do so.