I was born that way. By the time I was 6, I was saving up my allowance to ride my bike to the sporting goods store to buy the ultra-cheapest pocket knives, all of which are now gone. I just couldn't control my need to carry a pocket knife. I was probably the only kid in my Catholic grade school who carried a knife to school. It was a Boy Scout knife with three of four folding things, and the Scouts logo on the scale.
I did everything with that knife: built forts, whittled, roughed-up my bicycle inner tube to apply a patch. We had to learn how to do everything ourselves. My Dad said, "I had to learn myself, and so do you!" By the time I was in junior high I was building my own computers, and my SAK was an integral part of that.
i just always had a knife on me, so I did everything with it. And every time I had enough money, I purchased a new knife. I went through a stage of oversharpening in my youth, where the belly of the blade got bowed in. My uncle said, "You sharpen it too much. I'm taking the stone for a while. Ask me when you need it again."
Pretty soon I had pocket knives everywhere, in every dresser drawer, every coat pocket, in practically every room of the house. Then one day it hit me, there is something to be said for quality over quantity. I had a lot of knives, but most of them were worth zero. Now I'm grown up, and I've still got the monkey on my back! But now I look for a great value, not too expensive, not too cheap, although I have quite a few in the 100s of dollars range.
I think it's just the endless uses; knives are among the most useful things in the world. And skill in use and maintenance is valuable.