Google is constantly improving the search results. If factors, such as a low bounce rate and high dwell time, show that a site is popular and useful, why not rank it higher?
People tend to think in binary: A site is either spam or no spam. But spam is much more complex. A site can be 90% good and 10% bad. A site can turn spammy without their intention: comment spam, hacked sites. A site can pull out all the stops to hide their link buying. A site can be useful to have in index, regardless of some spammy behavior.
In order to judge if something is better, it presumes absolute reference points. In otherwords, google ranks the "productivity", generally. And then only later, refines the relative merits within a sub-class. (And if this was true, it would have nothing to do with Rap Genius.)
Avoiding the (questionable) debate on the productive capacity of planet-earth...the "model" of what customers' "really need" is questionable. Do they need (1) information that is factually correct?; and/or (2) do they need the actually meaning or interpretation of (1). And if its true a subset need (2) what is the ratio of (2/1)?
People tend to think in binary: A site is either spam or no spam. But spam is much more complex. A site can be 90% good and 10% bad. A site can turn spammy without their intention: comment spam, hacked sites. A site can pull out all the stops to hide their link buying. A site can be useful to have in index, regardless of some spammy behavior.