Wine quality is judged by an external group of fancy wine people who will determine your wine's future. If you get an Excellent quality rating, it's good for business. It's like Yelp reviews, mostly out of your hands but can make or break your business. So there is clearly a business benefit in trying to produce a wine that will get a good rating. While that seems self-evident – make good wine and people will like it – there is enough subjectivity in wine preferences that it makes this hard to do.