Simple choice of style. The purpose is to keep the handles from contacting the blade in the closed position.
Some folks use the second tang pin. Others, like BM, have a "kick" at the bottom of the edge... a sort of blocky part that sticks out for the handle to hit, instead of hitting the edge, and dulling it down.
FRom what I gather, there are other ways of doing it, those are just the two most common