I guess they can be. I have a wonderful Perry White Mag Dublin Blast, 1" diameter chamber and it weighs in at around 4oz, so not a jaw hanger, but jaw breaker ::
You can see me light up that baby from space ;-)
It dominates all English blends
My Randy Wiley Unigue has a chamber bigger than a coffee mug. I have never tried filling it all the way, since I only have 8 pounds of tobacco. But it is great for smoking complex blends because all of the parts get smoked evenly, I guess. Someone here once recommended big chambered pipes for complex blends, and smaller pipes for simpler fare. I think that there is some truth to that assertion.