There's been some great discussions online lately (and I recommend you go through the comments section too!) about the place of criticism and critics in the arts. As a publicist and producer, I have to say that critics are very important to me. Word of mouth is the best way to sell anything, including a show, and so I need reviews in order to pull quotes. The "Hey look at what people are saying about the show!" approach. As a producer, I do the same thing for grant applications and sponsor/donor drives, though it's more of a "Hey look at what these people are saying about us!" approach.
Critics are by no means the be all and end all to my publicity campaign, but they are one more tool in my belt. And the more "legitimacy" society gives to the media outlet that reviews my shows, the more importance I will place on the critic and the quote.
Do I necessarily agree with this way of thinking? That people need to be told by someone else whether they should see a piece of theatre or not? No. As a person who loves the theatre, I like to see everything and make up my own mind. I might read reviews before I see a performance of something, but it won't affect whether I go or not because I will always go.
But my job is to sell a show to people who aren't like me. People whose entire lives do not revolve around the theatre. People who need to know that if they are going to be spending $20-$25 on a performance that they will be entertained. You know, sane people.
And so, I go back to the people they can hopefully trust, either because of the critic or the medium they are involved with.