I've had a knife in my pocket almost every day of my life (except when flying) since I was about 10 years old. In the course of my employment, I work with 1/2" and 3/4" rope, and I prefer to have something that will get through them with a minimum of fuss, so my regular knives over the years have had blades of from 3 1/2 to 5 inches. When I have to be "dressed up" I carry a small pen knife, with a blade of about 1 1/2 inches or less. Even if I'm not carrying a sgian dubh, I have a small, very sharp pen knife in my sporran. I've frequently found the knife to be handy for a multitude of things, opening packaging, peeling fruit, shaving chanter reeds, sharpening pencils, etc. Even automotive repair. I ran an old CJ5 jeep for years. They can be as problematic as old sports cars ( and just a satisfying to work on.)
I've found carrying a knife to kind of a generational thing. Most of my younger (45 and under) coworkers do not carry a personal knife, and seem to find it a foreign concept.