Every year there's a new hot technique or equipment change in the Nordic racing scene. During the development of skating as a separate discipline, these changes were often drastic and meaningful. Some were doomed experiments as weird as anything from the Age of Dinosaurs. Others reflected the evolution of gear and technique to make skating genuinely more efficient.
The period of skating evolution got people in the habit of expecting change. It slopped over into classical technique and equipment as well.
Some changes have been more or less permanent. Skate skis settled in to a fairly consistent set of lengths and flexes. Poles grew to ridiculous heights and then settled back to a reasonable one. Classical poles grew, too, and settled back slightly longer than they were at the start of the process.
The funny thing is, within the narrower band of what has proved to work well, fashions seem to change from year to year, a centimeter or two one way or the other. Most of this is just fidgeting. It works better because people think so. It isn't different enough to be noticeably worse. It's still within the usable range.
If a racer tweak makes you cut your expensive poles short one year you'd better hope the trend doesn't favor longer ones next year. That's a good reason to have a couple of sets of poles for each discipline, so you can ski according to fashion without butchering something you have to replace for the next trend.
One benefit to racer tweaks is that they get hard-core skiers moving slightly differently from one year to the next. This might actually help reduce the chance of repetitive strain injuries. No one with coaching credentials has said so officially. I'm just pondering the notion. On the plus side, even if they don't do any measurable physical good, they probably don't do any harm.