This is a long thread. Anyway, I carry one just to have in case I need to cut something. And that happens with regularity.
Aside from that though, to be honest, I just like knives. The way they look, feel, and perform. It's just like any other hobby. Some collect golf clubs, some old tools, some collect coins. It's just an interest you develop when you begin delving into the history and lore of knives.
I don't carry one for self defense, although I have some that would cover that category. I carry a gun for that.
But there is something so much more personal about a knife. Just holding one that you liked enough to buy, for whatever reason, gives a sense of power. I can imagine that our long ago ancestors felt the same thing when they held a blade in their hands. It's a feeling that a gun just doesn't impart to me. Or a golf club.
It's like you can hold back all the darkness of the world if you needed to. Just you and your knife.
Silly I know, but that is the feeling that a knife in my hand, gives.
But hey, the one's that ask you why you carry one, don't really care what your answer is. They've already made up their minds that you're an extremist, full of self delusions. So why even play their game. Just say because I want to. And leave it at that. Chances are they'll never understand anyway.