Why does Higher Page Rank not allways give you better ranking?

[domweb]

But, but...isn't it like a penis? Bigger is better? Right?

I think people rely on it so much because it is the only easily quantifiable number that seems to show how important the page is.

SERPs are a concept that is harder to comprehend and harder still to measure easily.

Until a webmaster gets a good education from message boards and the like, he/she is going focus on something with a name like PageRank. I know I did. (I used to keep track of my Alexa ratings too).