Simple - because search results are ranked by overall relevance to the search, not by PR. Just because a site has high PR, doesn't mean it is relevant to the search you entered. Google has PR 10, but if I search for "pasta recipes" I don't expect to see Google.com appear as a result! Having said that, if two sites have very similar relevance in terms of keyword content and anchor text etc, then the one with higher PR will tend to do better in the results - but only if the other factors are equal. Howard
oceanline - to correct andriusk, PR is related to ranking, and is used in the method of ranking, however it is merely one of many factors.
A site is listed according to revelancy of keyword and PR LOL directory.submission1982 - that is "ranking" - as in the site's position in the SERP