Perhaps they do some (even most) of the time, but not always. E.g. I just read the review of Kane & Lynch 2 recently and it faults the graphics and how the cover taking doesn't seem to work every time, which I didn't find to be problems on the PC version, at least not for me (although I still agree with the overall score the game got).
It would just be more convenient if the platforms the review focused upon were easily identifiable with just a quick glance, keeping you from having to read the whole review to realize it doesn't really reflect the game on your platform of choice.
The Detail, a crime noir adventure in a modern American city. This is a city where cases matter, clearance rates matter, and on a good day even justice matters.