We look at weathering considering what the builder wants to represent. We use flashlights since many of the rooms used for model contests are not well lit for viewing models. These lights are needed just to see the model. Also, we assume, if a modeler puts a lot of detail into his entry he wants it to be seen . So flashlights are used to see the work to help us evaluate the model.
Some people disagree with the use of pen lights.
While this may be a valid point with more traditional systems of judging where finding faults might diqualify someone, our system eliminates this concern. We use them as tools for our evaluations and not weapons to destroy other people's work. Using a penlight doesn't give the right to anyone to be careless and obnoxious when viewing a model. Well nothing if you are proud of your work and don't mind having it looked at. But if you are lazy and still greedy for a trophy a pen light could spoil your chances.