It's (or it WAS) all chin - a bent pipe is not just a straight pipe with an angled shank. Have a look at the Peterson "Professor" shape and see how they balance a 1/2 bend with a heavier curved shank.
Not necessarily make it chunky - a Dunhill LC shape is not, for example, but when you look at a bent pipe, the lowest part of the arc on the bottom of the bowl is really never occurring in the midline of the bowl - it happens further back, which relaxes the shape and makes it less awkward (moving from a straight shank to the round bowl bottom).