The quick answer is so you know WHY you like what you like. Let’s say you like Napa Valley Chardonnay. So you go to the store and get a French Chardonnay, thinking it will be similar. But its not. It’s WAY not. Or you go to an Italian restaurant and they don’t have any Napa Chardonnay and you don’t know what to order. Or I tell you that there are some great wines similar to Napa Chardonnay that cost half the price if you know what to look for. In all of these scenarios, knowing that you like fruit forward, moderately oaked white wines would help you better find a wine you like. And there are just too many awesome wines out there to drink Napa Chardonnay your whole life (by the way, nothing wrong with Napa Chardonnay; just an example!)
Also, because I truly believe that a lot of people have bad wine experiences because they haven’t had it in the proper pairing context. There are so many fantastic wines and regions and makers and styles. But if you drink a big tannic Italian Barolo without a nice, fatty, palette cleansing rib eye steak, it’s going to taste harsh and bitter. But together…you’ll die and go to heaven.