Laws should be simple and fair. People should not be able to unwittingly break them by engaging in normal activities. Knives are not in themselves inherently dangerous, no kitchen is complete without some for instance. We should concentrate the law on preventing people from deliberately stabbing each other and it is already illegal to do that. Situations where it is reasonable to carry a knife are obvious to most right thinking people, the Police should be left to judge with the Courts to back them up.
At the moment the laws on the carrying of knives are hopelessly confused and complex. Because of hasty ill thought out legislation many people are unwittingly breaking the law by, for instance, carrying a life with a lock blade whilst walking in the country. Most good quality penknives these days have lock blades but for some reason carrying one can be illegal. If the law were simplified making it for instance "unlawful to carry a knife in a situation which may lead to a breach of the peace" then it could be left to the common sense of the Police and Courts to differentiate between those engaging in peaceful pursuits and those carrying knives in city centres or similar.