A lot of people don't like to buy the whole set, necessarily. If I list jewelry that matches in heartsabustin, I list the pieces separately, but put links to the pieces that match in the listing, if that makes sense. I have sold them all together before, but sometimes, they just want the bracelet, and I don't want them to have to send me a convo. Jewelry tends to be an impulse thing, and I don't want to drive a customer away because it's all listed together.
I think sets work better in vintage, where it makes more sense to sell the whole parure or demi-parure together (fancy French words for sets that go together. :D)