Just because the single search box works for Google does not mean that it works for everything.
Even Google provides advanced search options, and they are often the only way to a) find what you need, b) see what search techniques are possible, and c) learn the search tags that you can later use when constructing complex searches in that hallowed single search box.
The only thing more frustrating than too much information is not enough information.
Searcher’s block is a common malady afflicting people faced with no guidance about what kinds of searching might be possible.
If you don’t believe me, just try finding your particular (pre-ISBN) version of the Agatha Christie mystery Curtain in LibraryThing. There’s a single search box for you… I love LibraryThing, but I HATE finding old books that don’t have ISBNs and that have common words for titles. It took me forever to learn that if I just put information in the right order (and separated by commas), I could replicate an advanced search. In the mean time I’d gone through gallons of tea in an attempt to keep myself from pulling out my hair or dropping the project altogether.
I’m inclined to believe that the popularity of Google’s single search box has more to do with the algorithm running behind the search than with the box itself. If my catalog could rank keyword results as well, I might be more inclined to go that route. But it can’t. So I’m in no way inclined.