You're missing the point that organic results are also hugely influenced by financial motive. The underlying concept is that all information is biased.
A system that incorporates bias is vastly more useful than one that ignores it.
> The underlying concept is that all information is biased.
Right, but why add more bias if we don't have to?
Organic results are influenced by the content of the pages as well as their relationship to other pages. Sure, people spend thousands of dollars on SEO to make their page more attractive to Google, but at least they're trying to fit Google's idea of what makes a useful web page. With AdWords, money is directly influencing rank. Why is it good for Google to incorporate more financial bias than it has to?
A system that incorporates bias is vastly more useful than one that ignores it.