Cognitive dissonance. That's what's bothering you. Reality and your self-image are not in sync, and you are becoming aware of it.
Here, let me help you: You are a knife hobbyist. You have an interest in knives beyond just selecting a tool for a particular purpose. You like them. You enjoy them. They appeal to something in you. You joined a forum about knives, and even paid for a subscription. You, my friend, are into knives.
Your internal conflict comes from you having the idea that "I must have a legitimate need to justify these purchases. There must be a logic to it all." Well, good news and bad news. The legitimate need you have is to engage in an activity you enjoy. A hobby. This hobby, in fact.
The bad news is, you are spending money on something that is purely for pleasure but seems like there should be an actual useful purpose beyond that. There may be a useful purpose for your first 3 or 6 knives. Beyond that, you're a hobbyist / collector / compulsive spender / hoarder / rich guy with money to burn.
Just accept it and life will become simpler. You will buy what you want and carry what you want, and not worry whether there is any actual need or purpose other than the fun of it.