The problem is, no one ever gets the five year sentence, because anyone can concoct a plausible reason for carrying one (need it for work, just purchased it and am carrying it back from the shop etc). The carrying of knives is a very serious problem here, no doubt about it, and a problem without seeming rememdy, not like we can put an outright ban on knives.
Why is it a problem is the reason is indeed plausible? A legal system should take the least restrictive rule, and apply common sense - something I
love about the UK. I recall buying a kitchen knife from Sainsbury's when I lived in the UK, it came in a reasonably tough plastic cover. I remember thinking if I'd be in some sort of trouble (though no sane policeman would stop someone carrying grocery bags!) but then realised I'd simply say "I just bought it mate, here's the receipt".
On the last point, I remember reading, could have been health and safety gone mad type of urban legend, that the UK was considering banning large+sharp knives out of the professional setting because people cut themselves taking out avocado seeds, or some nonsense like that. In fact it's so nonsensical that I'm sure it was written to stir people up.
In Switzerland my kids go to the forest once per month with their schools. Part of the stuff we had to supply them with were folding knives with clips for whittling wood to stick sausages over fire. I'm talking 4 years old! I remember wondering with my wife if that's a great idea, until saying to ourselves "the Swiss are probably right, as usual"!