A lot of people still seem to think that SEO is a magic powder made by technical people for a couple hundred bucks. They think that marketing activities that took 2 full-time employees and an advertising budget in the offline world, can be replaced by a $100/month service in India.
Boy are they wrong.
Let's start by looking at what Google's job is: to provide high quality results for user searches. That's it. Plain and simple.
If Google does not provide the highest quality search results, people will use different search engines, and Google will die. It is of paramount importance to Google to be the best. This means that Google will not enter into any agreements or activities that compromise this.
What Google Does
In order to provide the highest quality search results, Google has to determine which websites are more important than the rest, and order them accordingly.
If your website is not better than all 10 results on page 1, then you will NEVER be there. Plain and simple.