Removing the availability of the weapons reduces the risk.
So what are you going to do, ban all knives?
How will I cut up my onions?
Shall we ban all cars too, as so many die in road accidents?
If someone intends to hurt someone, they will find a means to do so. Banning certain types of knives and not others is practically useless. If someone can't get a flick-knife, they'll just use a kitchen knife. Simples.
I'd imagine most stabbings are done with legally available knives anyway. Most people killed by cars are probbly killed by legally owned cars.
I was once threatened by a lad with, of all things, a door spring thing, y'know, what stop doors from slamming quickly? I picked up a handy brick to 'even the score'. What a daft situation, and what rubbish 'weapons'.
That door spring still cooduv done a lot of damage, if not killed someone. Shall we ban door springs? Bricks?
See, don't matter what you do, a dedicated criminal intent on hurting someone will always find a way round things.
Beer glasses made of safety glass would help prevent a lot of serious injuries, but there's no way the pub industry would suck up the significant extra cost, and no way the public would accept significant price rises as a result.