Popularity is not equal to relevance

Except in the case of advertising

Even if, hypothetically, company knows what user is searching for before user finishes typing a query, it does not mean company is going to deliver it to user

Company is paid by advertisers, not users

Company can deliver something _popular_, call it "relevant", make bank

"Popular" grows audience, good for advertisers

"Relevant" not necessarily good for advertisers, only good for user

Company serves its customers: advertisers

Company does not need PageRank to determine popularity, only search traffic (search query data)

(Of course a result could be both relevant and popular. But a result could also be relevant and _unpopular_. Company is promotes the former to the exclusion of the later. It profits by selling advertising services to advertisers, not information services to www users)