This is written mainly with video game reviews in mind, but the same holds true to some (although a bit lesser) extent for movie reviews as well.
There seems to exist this very common and widespread notion that the review of a work of art (especially a video game in this case) has to contain a summary of its first act. In other words, a brief explanation of what the story is about.
I don't really understand this. That is a spoiler, plain and simple.
And I really, really hate spoilers with a passion. If I start playing a game, I don't want to know anything about it. Nothing at all. I want the story to come as a surprise, for it to develop as I play the game, and everything being new.
With video games in particular, the idea in the story is not a deciding factor on whether I'm interested in playing it or not. I can't think of a single example of a game that I would have thought that it could be interesting to play, except that the summary in the review sounded so uninteresting that I'll pass. That just doesn't happen. (This might be the case with some movies, but very rarely.)
A review of a video game can be perfectly well written without telling a single thing about the contents of the story. (Of course the review can allude to the quality of the story at the meta-level, but without revealing any details at all.)
What is more interesting in the review is to know if the game is actually fun and enjoyable to play. The story can be a big part of the gameplay experience, but I don't want to know what the story is, I just want to know if it's good (in the opinion of the reviewer).
Many reviews seem to include this kind of summary just because it kind of "belongs" to a review, because of tradition or something. These spoilers are completely unneeded.