Not just "today". In late 00s folks at Microsoft Bing noticed that every time they'd release relevance improvements, Google within a couple of days would boost its search relevance just enough to stay a pace ahead. The running theory at MS was that they had a lot of gas in the tank relevance-wise, but artificially hobbled it, so that it's just above Bing's. Why? Because fewer people will click on the ads if the results are _too_ relevant. They'll click on the links instead.