A perhaps confusing question to those ignorant regarding the ways of the blade, but completely similar to any circle of people intimately familiar with a subject matter in particular, the terminology of knives is small, sparse, and commonly overlaps with knife enthusiasts, fanatics, collectors, smiths, and designers.

To answer why, or more importantly, what determines the complexity, depth, and diversity of terminology, one simply needs to look at and understand the depth and complexity of the subject itself - if it’s even that complex or in-depth to begin with.

The first, most obvious, and most important thing to understand about knives is that they are simple. They always have been, were always meant to be, and always will be, even with the advancements in blade materials, blade types, knife designs and materials, and knife forging techniques. The knife is one of the first inventions ever created by human beings, after all. The true nature of the knife is eternally unchanging and uncompromisingly simple.

Thus, due to the simplicity of knives, the depth and complexity of the terminology involved is relatively simple and straightforward. It was never meant to be unnecessary complex even among knife manufacturers that go deeply into the subtleties and complexities of knife steels, handle materials, knife types, lock types, blade shapes, blade hardness, etc.

Anyone who wants to gain an understanding of and learn more about knives, would do well to learn the terminology used by knife enthusiasts. They would practically need to in order to truly enjoy their passion for blades, as they must understand caring for knifes, maintaining them, buying them, using them, and many other things any blade enthusiast absolutely must know.

The knife community is a large and diverse, yet tightly-knit and bound community of users, makers, collectors, people who carry knives as part of what's called an EDC system they have (a very well-known term among the knife community that stands for Every Day Carry), hunters, men and women in the armed services, police, martial artists that train to fight and defend themselves with blades, and even criminals and unscrupulous types.

There’s common knowledge that anyone into knives learns and knows. One needs to know the basics of knives before they learn the subtleties and technicalities of knives, or of what little there are, really. Sharpening, honing, cleaning, using, and storing knives are one of the most basic and essential skills and bases of knowledge that one can develop, and this area of discussion is where knife terminology becomes commonplace, and overlaps frequently among knife enthusiasts.

Since the complexity and frequency of terminology depends upon the complexity of the subject matter in general, and since much of the terminology used, and the aspects of knives discussed in general are the basics of knife care, use, what kind of knife steels there are, different blade types that exist, and such, focused on education and the fact that knives are consumer products in the end, and such terminology is also necessary to know to understand and make the best decisions a consumer can make regarding the purchase, sale, maintenance, and use of knives according to the needs and desires of knife enthusiasts, collectors, and consumers in general, is the reason why knife terminology overlaps so readily and frequently in the world of knives.