On a poly chanter top the ferrule is definitely decorative. On a wooden top is may help guard against splitting. The top of the chanter is the part most subject to dampness. My Dunbar chanter is a combo. The chanter body is african blackwood, while the top is poly (no ferrule). I did order it with a sole, simply because I like the look. The sole does, however, have the slight advantage of elevating the end of the chanter off the table top. When I'm not at a table, and resting the chanter on my leg it serves to keep the sound hole up and clear.