Thats because in the uk almost all cops are not armed.
It takes a brave man to take on a guy with a knife and even when there are several of you with clubs you still have to be the type that isn’t afraid to get physical, give them their due.
All cops should be brave, when they aren’t they just stand back and gun everything in front of them, like we see so often in America and we see so many innocents and dogs gunned down because the cops just arrived and haven’t even bothered to learn who is who yet, or who called them in the first place.