All plays are reviewed. If the replay official sees enough on his first review then there is no reason to stop the game for the most part. Now, there have been some plays where I agree that the call on the field was good but it wouldn't hurt to stop the game just to "review" the play to ease the tension of the fans who may be in disagreement. The replay official is already in agreement but calls for the "review" so that there isn't any controversy. I call those
PR reviews.