You do it because your tastes are different than others. Just because it is labeled as the best restaurant doesn't mean it is the best nor does it mean you will like it. There are still plenty of out of the way places to explore. On the other hand, if you don't have time to explore it can help you narrow down your choices. Not to mention of you search for "best restaurant at place x" you'll get a half dozen different ones. It is just a tool, just it wisely.