Most laws like this also ban certain types of knives, most commonly balisong/butterfly knives. Most places admit they're not more lethal, it's purely because they're intimidating.

Australia is one of those places, and right now there's a push by the local MSM to try and crack down on "zombie knives". You know, the impractical decorative shit? Like it can still cut, but it's no worse than a normal knife/machete. It just intimidating.

These bans reveal the truth of pretty much all bans. It's not based on rational belief, it's based upon irrational fear.