brainwaveUnless you have need for a more portable sickle, karambits are mainly for combat. I assume most people buy them because they're "cool", seeing how they don't really do utility work any better than a more traditional blade.
brainwaveI keep a Fox Karambit in my waistband (I really shouldn't, since it's difficult to deploy from there) for self defense. In closed position, it's extremely useful for boxing and hammer-fist attacks, and complements kickboxing well for self-defense. The retention ring is extremely useful for striking. "Kuya" Dough Marcaida has great demonstration videos on the most effective ways of using a karambit for self-defense.
I happen to use mine as a letter and box opener since the blade is thin and sharp. But I keep in mind that this is mainly a self-defense weapon and don't use it on anything thicker or harder than flesh.
brainwaveIts usually one of two reasons, self defence or collecting but it still does have the same utility as a normal knife minus stabing for the most part
brainwaveIts for self-defense and shaped to slice and dice like cockfight blades. If your fascinated by it, learn to use it. Its a fun knife to master. There are some youtube tutorials on Karambit self-defense.