defense knives
There are several good reasons to carry a knife:
1) there are many places you can't take guns
2) if you have a smaller one, it's not considered a concealed weapon
3) for many years I was too young to get a concealed weapons permit
4) knives are cheap; guns are not
5) knives are small and light, guns are comparatively big and heavy
6) many people flip out if they find out you have/carry a gun. knives, not so much.
examples/explanations to the above:
1) I go to school at a private university in Cambridge, MA. No firearms whatsoever are allowed on campus, and to even have one in boston proper, you must belong to a gun club (about $300 a year). In high school, I was an Explorer (ride along and train with the SO). We couldn't carry on duty, but we could have knives.
3) Young people get mugged too, and it was common knowledge in my school that I carried a knife (blade just short enough to fly under the 'no weapons' rule). I have no doubt that this deterred more than one confrontation.
4) Being a college student, cash is short. I've got guns anyway, but for those many for whom guns are unaffordable, there are many decent knives available for 15 bucks, and about a jillion and a quarter for less than 50.
6) going to scool here, I've come to take it for granted that uneducated people (no matter that they're going to a top-tier college) are stupid about guns. They're utterly convinced that this is a realistic scenario: they walk into a room and see a gun laying next to a round of ammo. The gun (it's a glock because that's the only kind they've ever seen live) will immediately assemble itself (if needed), hobble over to the round, load it into the clip, insert the clip, rack its own slide, and shoot them in the face 4 times.
Point is, since they don't know about guns, they're freaked out to the point of paranoia about them. Should I carry here, word would likely spread with the first person who found out (and living with various people over time, it's inevitable that someone would). So it's a simpler deal to carry a knife. My anecdotal 2 qirsh.