@Fred931 Simply because things change so fast that this week’s Best is next week’s Better and next month’s Good.
Okay, it isn’t quite that quick, but considering the number of components that they sell, they would have to hire a whole crew of people who did nothing but keep those ratings updated. And the fact that Intel changed their naming conventions, thus making it harder to get the best CPU, doesn’t help.
As for motherboards, there is not universal “Best” there. Some people are fanatical devotees of a particular chipset and won’t consider switching even if the competition is faster. Some need a particular set of slots. Do you need RAID, 7.1 sound, or eSATA? “Best” is too subjective there.
Cases are a matter of aesthetics, cooling, and ease of access. Most are roughly the same size with the same number of bays, but some have more places to mount fans, some have easier-to-access drive bays… you really have to research a little.
That site really is meant for people who already know what they are looking for.