I hear you, but the questions this post makes me ask are-
Why does Kobudo include nun chukkas, oar, gig pole, tonfas, small scythe (don't remember what it's called). Those are all fishing and farming tools.
What did fisherman use for knives if they couldn't get metal? I can't imagine any fisherman not having a knife.
I guess that's what I'm imagining here- someone trained in self defense getting robbed somewhere by a poor peasant with a small fishing knife of something fashioned from broken glass or some such. The "old masters" said karate wasn't for fighting. It is for a life or death situation. If I'm going to rob you, I'm going to have a weapon. I'd be stupid not to. It still seems crazy to me that karate wouldn't be expecting a weapon if it's meant for that type of situation.......
Lol but if the poor couldn't get knives that would explain why we see examples of defense from the bo in the old katas!
All good questions. For the metal: there was certainly
some, imported from outside (China first, Japan later) including the kama. Kobudo includes them because it was - like -te - a rich person's hobby, not a peasant. Or a warrior/guard's.
Not an expert at all, but not sure fishermen used knives. For example, the oldest fishhook known to us is carved from shells and it's from Okinawa, and a shell would come handy to cut a fish is needed, or rocks to sharpen a wooden spear to catch bigger prey.
For the rest, I think it's just down to probabilities. Almost anything can be used as weapon. For example, it's forbidden in many countries (at least here in Europe) to carry a knife, but nobody objects to a screwdriver, and yet you can easily kill with one. Even a fork is a deadly weapon in the right hands. There's no martial skill that can take in account all the possibilities. You get to develop calm under stress, speed, timing, evasion and the likes.
Besides, then as now, people who ended up trying to mug others weren't the sharpest knives in the drawer, and unlikely to have much training. -te teaches you to avoid attacks by untrained opponents, exactly because he will telegraph his move, display excessive momentum and imprudent commitment, and so on. It would not really work that well in a battlefield full of armed people with combat training, but it seems likely to do against your average mugger of the time.