I guess they didn't discover that screwdriver can be just as efficient and its not illegal to carry it.
Found this few minutes ago.
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Anything can be illegal to carry (uk law anyway), screwdriver is no different. The limitations on carry apply to intent. A pair of gloves and a hat are pretty innocuous until you're out to burgle a house, then you are guilty of 'going equipped' an arrestable offence, if you intended to use the items in the commission of an offence.
A screwdriver is no more legal to carry than a Survival Knife, if you're in a nightclub with a 4'' screwdriver, then the court can draw proper inference that you were not there to fix the door handle.
If you are walking home back from a week in the sticks, with a 9'' hunting knife, then it can be successfully argued that you have reasonable excuse to carry it.