Is it though? They have sooo many sources of input, embedded ads everywhere, social buttons, gmail, calendar, documents, photos, android, blogger, youtube, google+, and probably others that IDK, that search is just one---and probably a less important one---of those. As a means to show ads, again, they have uncountable spots all around the internet that they can place ads, and many google apps that one might be using, that the search results page is again just a slice of a big pie.

Or maybe they figured that most people do very simple searches nearly all the time.