A lot of agencies use PR and Alexa rankings to negotiate rates.
negotiate rates for what?.. link buying for Pagerank?
Advertisements.
I'm not entirely sure why you're being so hostile since you're clearly not familiar with the content being discussed.
PR can affect your ranking on searches overtime as mentioned in the article.
Focus on your users, not on search engines. Whether you have a high PR or not has no effect on your users.
If users can't find you, you won't be getting any more of them. Engineering is fantastic, but not much use without people knowing about your hard work.