The way you put this makes it sound like the process of design you described does not create the ecology you described, but it does. Why do you think "the youth" have different tastes? Fashion is constantly being dreamed up by influential brands, and they attempt to impose their vision of the future in such a way that it will become the new norm. This process doesn't just happen by itself. At the same time, outsider styles emerge and become popular by virtue of doing something different and catchy, it is a constant pursuit of holding the banner and commanding attention by many parties. Those who simply chase the style of the day will always be out of the loop because by the time they deliver it's already the past.
Of course the process is not the course of nature but no single brand has the power to design it. Instead, politics happen innovations happen new brands and new lifestyles come and go and each and everything is designed bit by bit but there's a no grand design. There's of course a literature and know how that piles up and the new designs takes cue of those but still, there's no grand design. It just evolves over time as people respond to everything that happens with the world. It doesn't happen by itself as a biological process but it does happen by itself as a sociological process. The biology just defines the pace of it.
