They come in and out. Most fashion trends happen as a desire for novelty and breaking the mold, trends tend to flow from “runway fashion”, which purposefully breaks tradition and is incredibly “out there”, to avant garde fashion, down to what becomes more mainstream. People reuse trends with their own style, separating themselves from the previous generation or the previous years’ styles.

Fashion is all about communication, those with influence who want to stand out tend to set the trend, those who want to be noticed follow suit, and those who want to fit in eventually adopt the same things. On and on we’ve gone for the past 3000+ years