It's merely a choice of style.
Just like every other trend. Trends move in cycles. However, the Internet is still very young. So we have no idea how many cycled trends there will be.
As new technologies or methods arise, so will new trends based on those methods or technologies.
I personally think that everyone's style will stick with Web 2.0-ish appeal for a while however. Mainly because of the graphics, and functionality that accompanies it.
For quite some time, people were driven by mechanical styles, etc, because this is the style the 2advanced (one of the most popular design firms on the net), had set forth as an example of standard.
People still follow 2A, but not as much as previously. Mainly because people are growing up, technologies are changing, etc.