With regard to "knife crime" it's patently obvious that knives don't commit crime. People do.
There's a ton of legislation these days about possessing knives. Yet each successive law that's passed seems to have little effect on this epidemic of stabbings. How can that be? It's fairly simple. The problem is not the laws, it's the implementation of them. To detect all those oiks that go around with knives illegally, you have to have police officers on the streets who will stop, search and arrest those with knives. Ideally before they plunge them into someone. However the routine patrolling duties of police officers these days has all but disappeared. Any routine patrolling that is done is by PCSOs. Who don't have these powers. So, really, despite a ton of laws, you can carry around your knife illegally with near impunity.
Once there's been a stabbing or two in an area, the senior police officers will get a bit worried and put on a special operation. Calling it something like reassurance patrols. Which entails, for a limited period police officers patrolling the streets and doing some stops and searches. In effect, what used to happen routinely now needs an organised operation to occur. It also smacks of shutting the barn door once the horse has bolted.
It is, of course all down to money. To get those police officers out on the streets instead of investigating name calling on social media and the like costs money in overtime. Something they are all reluctant to do. Let's face it, these days it takes riots to see cops on the streets.