Running arbitrary JavaScript on your server will likely cause performance, security and compatibility problems. It's not practical at large scale, and it's not something that would "fix" all the use-cases anyway.

Also, very few companies and no individuals will have the same technical capabilities as Google with it's horde of developers, years of experience in the domain, billions of dollars and ability to control everyone's visitor stream. They shouldn't be the only company that can effectively innovate in this field.