That's it, people like it. If people saw that content in lots of different places before they'd leave ehow in their droves, user metrics would reveal that and they'd fall down the rankings.
It's all about what people like.
Not sure where you are but in the UK we have a TV soap called Eastenders......it's not my cup of tea by any stretch of the imagination but it gets massive viewings 5 nights a week. Most people like it - Google is giving users what people say they like.
If people got bored of Eastenders they'd stop watching and the BBC would drop it in a second. Same rules apply in Google, in my view.