Because clearly knives can't be used for anything other than self defense/assault
does that mean they can't be used against you? no
still a bad idea, no matter the purpose. (unless you're loving hunting or something OBVIOUSLY, we're talking general citizens here)
Knives are tools, not weapons.
a tool that can be used as a weapon then, that makes little difference to my point
basically, if you have a reasonable excuse to carry one, that's fine but still risky. if you're carrying it just because, or for self defence, you're an idiot (and breaking the law where i live)