There was a time when the neck knife was a relatively new concept. They became extremely popular extremely quickly. I’m not saying nobody had ever hung a knife around their neck before; I think I first became aware of the concept when I saw the old 1942 version of The Jungle Book in which Mowgli purchases a knife (a “tooth” like a wolf’s, in his eyes) and slings it over his shoulder, wearing it in front of his chest. This made sense to me; if you don’t have a shirt and you barely have pants (and no pockets or belt), of course you’d wear your knife that way.

When neck knives suddenly came to the awareness of the “tactical community,” however, they solved a different problem. For as long as there have been tactical knives, tactical knife users have been trying to answer a very specific question: how do I carry this thing? When the Buck 110 folder was pretty much the standard by which large, potentially weapon-capable “pocketknives” were judged, the fact that you could carry the knife in a sheath on your belt was a big part of why it became so popular. You didn’t have to have the knife deep in a pocket, where it might be too heavy or might just be inaccessible. It was right where you left it and right where you could get at it.
The first clip-equipped tactical knives (such as those from Spyderco) answered a question most knife owners didn’t realize they were still asking. Instead of carrying the knife in a belt sheath, you could just clip it to your pocket, most often to the right front pocket (if you were right handed). This made the knife more accessible than ever. The big issue, though, was that the knife was still very visible. Whether on a belt in a sheath or in your pocket with the clip visible, anybody who looked at you could tell you were wearing a knife.
The disadvantages of a visible knife are many. If someone intends to attack you and they are observant enough to notice the clip or sheath, you’ve just told them where your go-to weapon is. If you’re somewhere that law enforcement is inclined to hassle law-abiding citizens over their knives (and sadly, there are many such places, particularly New York City, which is notorious for persecuting knife owners), a visible clip is a big problem. There’s also the possibility that a dishonest person could clam you threatened them with your knife when you never took it out of the pocket. The clip tells them that you have it and gives them this potential weapon.
Neck knives solved all of those problems, and an another one that modern man shared with 1942’s version of Mowgli. If you’re wearing clothes that don’t have pockets and don’t have a belt, you can’t use a clip or or a belt sheath (at least not easily). Some people do try to get by using waistband carry for their clip-equipped knives, and this can work. It means the clip will be too loose on most pockets (because the fabric of your pants is usually thicker at the waistline), but lots of people carry this way. Still, the neck knife provides a more attractive option, especially for light summer carry, because all you need is a shirt to conceal the knife. Especially if your shirt is untucked, all you have to do is reach up under the shirt line to access the knife.
The neck knife does have some disadvantages. It swings around on its chain or cord with the movement of your body, as any necklace or pendant would. That means that depending on what you’re doing, it may not be exactly where you expect it to be when go reaching for it. This is especially true in any kind of grappling or groundfighting scenario, in which you’re horizontal and possibly fighting someone off you. The neck knife will fall wherever it is inclined to fall with the work of gravity, which might mean you have to go hunting for it in order to find it. Under stress, especially if you’re fighting someone off you, this would be extremely undesirable.
Another issue with neck knives is that you are very limited in what you can realistically carry around your neck. The weight of a knife quickly becomes uncomfortable when you suspend it from your neck, so you’re limited to relatively small, light blades. Even a light knife like this plastic handled paring knife, however, becomes a problem in terms of length. A knife of this length isn’t suitable if you’re relatively short in the torso. You need quite a bit of “chest real estate” to keep the knife from printing when you move. Because you must keep both weight and length in mind, the field of possible neck knives gets trimmed considerably. (Obviously, some… ahem… people have more to work with than others when it comes to concealing knives in the chest area.)
We’ve known about the advantages and disadvantages of neck knives for a long time. What I realized recently, though, is that you don’t hear about them very often anymore. The most popular knives on the market aren’t neck knives, to my knowledge, and I don’t know of any of the big names in the tactical field advocating for neck carry. Yet lots of major manufacturers still offer neck knives, which must mean there’s still demand for them. After all, they wouldn’t make them if there was no hope of selling them.
So where does that leave the neck knife? Is it obsolete? Does it still have a place in the tactically minded person’s arsenal? Like so many things when it comes to blades, it’s really a matter of personal preference. If you keep in mind the advantages and disadvantages of a neck knife, it’s really up to you whether you choose to carry your blade that way. Given the good and the bad, I don’t think it would be fair to say these knives are obsolete, at least not yet. Only time will tell.