This is probably going to get me flamed, but if you are going to carry a weapon, and the Sgian Dubh qualifies, shouldn't it be something that you can use.
Not a flame, but IMO a sgian dubh's a tool, not a weapon, rather like a utilitarian pocket knife. As such it does need a live blade to be of any use.

I've always been skeptical of the idea that the sgian dubh was derived from some sort of weapon. That would imply that in a country that developed the four-foot-long claidheamh mòr (claymore) and the Lochaber axe, during a time of reivers, highwaymen, intergenerational clan rivalries and blood feuds when people went armed with broadsword and dirk everywhere (inlcuding to church), people expected to defend themselves with something akin to a paring knife.