Let me start by saying that I think the act of accumulation is genetic (i.e. people are driven to accumulate something). Not being wealth driven to the point where that's all we focus on we turn to other things to satisfy our urge and knives are a token. We use them for keeping score, to provide comfort, to bring joy, and just to have. We learn from them, study them, fondle them, etc. Cheaper than some things, easier to keep close than others, with less regulation than most weapons, capable of being useful (and for extraordinary lengths of time), some have historical or functional features that interest us. There's no shortage of knives unlike WWII combat aircraft for example, and everyone uses them. Until recently it was socially acceptable (and expected) in every society to have a knife of some sort in every persons possession 24/7.
A knife is one of man's oldest tools. Deep inside we have an affinity for the usefulness of a sharp blade. Even people who look askance at those who carry a knife cannot go thru a day without using one.
I was given a Barlow knife by my grandfather somewhere around age 6. I bought my first "hunting" knife (a Case fixed blade) around age 10. They were tools I learned and used. I bought my first custom knife back in 1987 from an unknown guy named Chris Reeve. I still have two of those three. I've used knives all my life, hunted, fished, worked on cars, made tools (including knives) and collected other stuff. But as I get older knives, their stories, manufacture, variety, and uses fascinate me.
I don't have any specific purpose to my collection. I have had; I went years trying to collect one of every pattern of Loveless designed knives. But now I just pick up knives like pocket lint, and then I study them. (A good example can be seen in this Traditional forum thread:
https://www.bladeforums.com/threads/a-blind-squirrel.1658601/ ). I have knives laying everywhere in the house and shop. But they're more fun than crossword puzzles, they keep my hands and mind focused, and playing with them is better than work.
Don't worry to much about why; collectors, and collections, evolve. Welcome.