Many if not most folders carry at least the pretense of being useful for SD, both for buyer and seller. While it is not an everyday occurance, it is'nt unheard ofl for someone to use a knife to ward off criminal attack. If nothing else it is interesting. If we really thought of knives as strictly tools there woud be no bladeforums. I doubt that there are 'hammer forums' or 'screwdriver forums.'
Regarding black blades, it appears popular to dis them, but there is a reason that most weapons used by LE, whether pistols or batons, are made black. Black does not draw the eye, which is always an advantage with regard to element of surprise. And having a black blade does not hurt in any way, at least in terms of function. If you don't like how a black blade looks, don't buy a black blade.
Regarding flippers, I still haven't had anyone explain to me why so many people think that a finger guard is needed on a fixed blade but not a folder. I don't use flippers for opening. I look at it like a seat belt. Sure, you can drive your whole life thru and never need a belt, but you still wear one just in case. Likewise for a guard.