I disagree. Outside the startup world, a lot of SEO is done simply to drive traffic to you so that you have chance to convert some of it into paying customers. All the small businesses that pay SEO companies to spam the shit out of the Internet don't do it for ad revenue, they do it just for organic traffic.
This motivation won't go away as long as people can use the Web to make money, so we're stuck with the pressure to game search results.
Maybe I should have differentiated between link-farm type SEO and web marketing. The former is more likely to cause people to abuse the system because simply getting people to visit your website or click a link provides monetary compensation. If you drove traffic to your website I could make a hand-wavy free market argument that if your product wasn't good, it wouldn't sell and you wouldn't have money to pay someone to drive traffic to your website. I fully accept that its my own opinion.
This motivation won't go away as long as people can use the Web to make money, so we're stuck with the pressure to game search results.