Answers (1)
Because they are not three button gloves. Three button gloves don't have three buttons, they are called that to distinguish them from other gloves. High fashion does not have to make sense, it is all made up so that the "in crowd" can tell at a glance who is one of them and who is not.
mentalfloss.com/article/12424/why-cant-you-wear-white-after-labor-day