This is probably a good reason for the success of Ebert and Siskel. The viewer knows (knew) the tendencies of each of the men to like or dislike different kinds of movies. If Siskel liked a movie but Ebert didn't, or vice versa, you could use that information to decide whether you might like the movie. Maybe you like Gene Shalit. You would decide on whether you like a movie based on what you know about him. You might even decide that, because some reviewer doesn't like a movie, you will.
The same thing applies to on-line reviews at IMDB, Rotten Tomatoes or Metacritic. You decide to watch a movie, not simply because it gets a good or bad review but you consider the source of that review in making a decision.
Why do people not take the same things into account when they read a review of some photo equipment in a magazine or on-line publication?
If people can read a review or a press release about a movie and say, "That's nothing but a puff piece," why don't they do the same when they read an article or an advertisement about photo gear?