IMO
It is not that uncommon for people to carry a knife. I do not understand why that would not be OK (especially for self-defense.) People do so for many reasons. I remember my Grampa carried a small one. He probably carried one since he was a kid. Every now and then he'd take out the knife to, oh I don't know, slice something off the bottom of his shoe, or cut rope or something when going to the city dump or running errands on the weekend or loading stuff. I think he even used it to clean under his nails iirc.
Well anyway.... just some examples of why some would carry a knife.