When one shoots primarily the same kind of thing and has good control over the lighting, it is easy to get consistant contrast ranges. Using development expansion and contraction can also keep a negative in the grade 2 paper range. Graded papers are easily pushed or pulled one grade using different chemistry - All these have been mentioned - There are those situations where the light meter lied - lens flare in the lightmeter (even in the expensive and good ones) - some unusual lighting challenge. Now your negative is hopelessly flat or thin. So VC paper is probably the only thing you can use. The frequency of occurance of these situations is less for those that have many years of experience. I am still building that experience myself. The good news is that I don't look at every scene and say - "I already shot that one" It is in the shooting of these scenes that the need for VC paper can be reduced. Dodging and burning will always be required at times as manipulation to get an image to conform to what we visualize the image should be.
Frank