Good subject!
I enjoy knives for a variety of reasons... I am a mechanic & machinist and I need, no REQUIRE quality tools, be it my snap-on ratchet or my Bridgeport mill or my good quality knives. I buy them as investments (wether I ever plan to sell them or not). I buy them cause I need to buy something with my spendin' money, might as well be something I really enjoy as a hobby but at the same time its justifiable as a tool so I can feel better about purchases.