It's all about page views, people want their views reinforced so they will go read reviews to support this. So a popular franchise will obviously have a lot of people who 'know' the game is going to be great before they even touch it and all they want is for people to tell them how great the game is.
Sure some places are worse than others when it comes to this pandering but it's largely the reason why review scores in general have risen over the last 10 years. It used to be a mediocre game would get a 4-6, and a good/great game would get and 8 or 9. Now mediocre is 7-8 with good, great being 9-10.
Just look at the whole Uncharted 3 story where people went ape shit because someone gave the game an 8, instead of 9 or 10. It boggles the mind.
tldr; scores are stupid.

