Firstly, consider that what we think of as a necktie - a long, vaguely rectangular piece of fabric meant to be knotted (usually in a four-in-hand or a full- or half-Windsor) and allowed to hang down over the shirt front - is a product of the late 19th century, and only really displaced other forms (the bow tie, for instance) in the early 20th century, largely because it was more convenient to tie and wear. Human beings have been wearing neck adornment for a very long time. The English-speaking world has been wearing them on a more-or-less regular basis since the 16th century in the form of a ruff. Originally, they may have been intended to protect the shirt, but by the mid 17th century a new accessory, the cravat, had been introduced. Variations on the cravat would dominate western fashion for the next two hundred years or so, made from a bewildering variety of fabrics and colors and tied in innumerable ways. I think we can say with a fair degree of safety that the necktie has been a primarily fashionable garment for the last 250 years at least.