The simple answer is no, but they are highly recommended. When not using a carb cap, all of the air will go directly into the intake of the banger. When this happens, your dabs will not have airflow directed over them and tend to conglomerate over to a corner. A carb cap ideally will help direct airflow right on to your dabs which allows them to get pushed across the bottom of your banger, which allows the entirety of your dab to get properly heated. You also kind of turn you banger into a convection oven when you cap it, since the heat is not allowed to escape from the top of the banger. So no, you don’t need a carb cap, but you will get a much more satisfying hit and won’t need as big of a hit.