[T.G]

People remove it for various reasons. I've found that it does not cook away and I personally don't care for the texture of what remains. Depending on the way the ribs are cooked, it can become tough and can detract from the food. Some people remove it for the same reasons that they remove the heads from fish - presentation and "classic gourmet" plating styles. I know some people who marinate the ribs beforehand and it will serve as a partial or even full barrier to a marinade depending on soak time. It's also questionable as to how much seasoning from a rub will penetrate through the lining. As for smoke penetration, without doing a side by side cook of ribs with the membrane and ribs without in the same pit at the same time, the equal smoke penetration theory is nothing more than that, a theory.

There are many ways to cook the same thing and end up with equally good, abet different results. Some people like "dry" ribs, some people like them sauced, some like them in a caramelized sugar style. Some people cook them with the membrane, some without. None are "wrong" and to prefer a method or style is simply personal taste.