And yes, ties when taken as necessary to be "proper" are vanity in that common use of the word. Wearing a piece of silk tied in a specific way (using various methods) for no functional purpose cannot be anything but vanity. The question is how important one ranks it. If it is a requirement of a job or situation, fine, we all have to engage in vain activities in some situations, but it should be properly understood and not overly praised. That is essentially what this thread is about isn't it? Being overly concerned and judgemental about appearances beyond modesty?
In defense of the tie, it has been a part of western dress in one form or another for centuries. It's purpose is to keep the neck warm. Originally, this was done with a cowl and a hood. You can see secular people wearing this in the illustrations of the Canturbury Tales. Monks, of course, continue to wear them. In the renaissance, the cowl gave way to the high collar. To avoid chafing, some cloth, often ornamented with lace was added, and it also filled the gap between the collar and the shirtneck. When the collar dropped in the 1600s, the cloth was left exposed, but still encircled the neck and dropped in front of the shirt, either with or without lace. That remained the fashion through the first half or so of the 19th cent., minus the lace after the French Rev. The silk tie was a thinner version of the same, made popular, I think, by Napoleon's Croatian troops.
If you have worn ties in the summer, you know they insulates the neck. So, it is not purely vanity. Perhaps in this era of central heating and air conditioning, clothes themselves will eventually be a vanity.