More than likely it did not come that way. It offers a protective layer during the long periods of cooking. Although it will not render, it will help keep the meat moist and prevent the meat from becoming overly bitter or having a too strong a smoke flavor. OK, we have now selected the best brisket and trimmed it to perfection. Now it is time to get to seasoning.
Some folks choose to marinade the brisket.
When cooking a large piece of meat that thick, this is not effective. More about that later. We use a dry rub. It is called dry because we use dry spices to shake, sprinkle, douse, cover, etc., the meat and then rub it into the meat. Not heavily though.