Because large companies(with nice Ad-Words budgets) are treated extremely nice both by the Ad-Words folks and the organic search algorithm folks. They are being favorized at the cost of small businesses that spend too little or nothing at all.
With each passing algorithm update Google is removing more and more small business websites and replaces them with bigger companies ( so called "brands" ) that often times offer worse services but spend more on marketing ( AdWords ).
Adwords was a fantastic customer acquisition tool for me and, in the early stage, drove 80%+ of my business for a relatively small cost of acquisition compared to traditional channels like direct mail. In fact, there is an entire industry dedicated to helping SMEs build and optimize their SEM. I can't remember the numbers exactly, but they make up a sizeable portion of Google adwords revenue.
So I'm going to go out on a limb here and say that you and the google conspironuts that are crawling all over this thread have no idea what you're talking about.