I've done a good bit of work with horn, and you can still find cups , buttons, and other things made with it. Despite the similarity to plastic, however, the stuff absorbs moisture and moves and softens under heat. A light horn cup that's turned and assembled with a mortised-in light horn bottom will likely warp and begin to leak after a few years, step on it and it will crack. Real plastics, like Bakelite, pushed horn out of common use in the later 19th century.

There are still people working the stuff, though, and doing very nice work. Mostly powder horns for people hunting with flintlock rifles, but other stuff as well. Check out the Horners Guild