I don't disagree that there isn't anything wrong with carving in public. I don't disagree that there are plenty of people who are quite at home carving in public and have never been bothered by do-gooders and the police. But I would venture that they are not in high population areas with high violent crime figures and youth problems. I see police daily patrolling and stopping youngsters in my area. Often they are searching them and removing items from them. As much as I may well be within my rights to use a blade in public for a legitimate purpose, I don't need the hassle of explaining it to countless police officers these facts. So I use a bit of common sense and save such activities for when I'm in a more understanding area, such as the leafier areas around me.