It's called dark patterns as GP mentioned. They're financially motivated to improve [Yes] clicks, so they just remove [No]. It's completely Web-legal and Web-ethical.
IMO, something should have been done when A/B tests became normal(mid to late 2000s). That ship had long long sailed, but I believe that alone require independent ethics board if it is happening outside the Web. It should not be something easily handled with a blanket waiver in shrinkwrap EULA.
