[Screens aren’t for tobacco pipes. ]
Let's try to put order for giving the correct information to people who are inquiring, particularly if they are beginners and if they have trouble with suboptimal combustion.
Provided screens are not used by the great majority of tobacco pipes users and that are for the most part used for other types of smokable products, there are screens/grids which are designed and used for tobacco pipes. If you to the Paronelli online shop, which is a reputable tobacco pipe only shop, they actually do sell brass grid for tobacco pipes with the specific indication of "ALLOWS YOU TO KEEP AN OPTIMAL COMBUSTION" and other tobacco pipe shops also sells them for tobacco pipe use.
This is not to say they are necessary but as I proved by myself can improve tobacco combustion. Can I achieve the same with proper drying and packing of the baccy? Yes and actually now I improved my packing technique I am using less and less. But there is nothing wrong using them in tobacco pipes and actually can help a beginner while learning the proper drying and packing or can help in situations when the baccy is not completely dried and you don't want to wait too much for drying.