Well there you go ruining the surprise. The bump is the point. Adds some body to an otherwise flat fly while retrieving. While thread can perform the same function, thread can't be adjusted. With a small float stop behind the bead you can adjust where the bump will be. Depending on the location of the bead and the length of the marabou it could keep the tips flared even on a retrieve. Not to mention the crystal flash or other stiffer material tied in with the marabou that would stay flared with the bead on a retrieve.

I agree though that there are materials that are much better served by the bead. I didn't think about them. Bucktail with an adjustable bead would be a killer way to tweak and fine tune a hair jig for water condition and what the fish are looking for.