People are conditioned to think Search has to work online. This was true when Google was created. No one had the processing or memory available on their desktop to search an entire index of the "useful" web. Not anymore. How large is a "useful" index of the web today? And can it fit on your laptop? The answer is yes. Can the entire thing be queried fast? The answer is yes. As an example take the entire stackexchange…
I don't think search is as simple as grepping a ton of files. Search Google for "movie where people can't have babies" and the #1 result is Children of Men. I think that's one area where Google pulls ahead of its competition is accurate results to vague queries like that and I think you need a lot of collected data from searches to provide that.
Edit: Oops turns out its 11 years old. Better make that the last two decades then. I'm gettin old