Most dealers don't make knives. I am not a knife maker. Most knife makers are pleasant and gracious and enjoy the public, but the ones who don't want to do shows shouldn't. I guess the explanation is like this. None of us like to feel limited in our abilities.
Many knife makers make a wonderful knife and a lousy sheath.
They want to think they can do it all. If you can't make a good sheath, find a sheath maker who can. If you don't like doing trade shows don't. Find a dealer who will be happy to promote and distribute your knives. Find a dealer who specializes in the type of knives you collect or make.