They just want more control over the Internet, and the ISP's want to make all content companies pay for transferring their data through their pipes. In the minds of ISP's, who so far have lived off ripping off customers with SMS charging, they don't think it's fair that people get to use e-mail or apps like Whatsapp for "free". They want their "cut".
Payment wasn't the reason that the US, UK, Canada, etc... aren't signing, it's the idea of opening up "Internet" governance into an ITU treaty. Once you start mixing Internet and telecommunications governance, you open the door to a treaty that would force countries with a strong free speech tradition to enforce the censorship laws of other countries.
