Happens in the design world too. Look at the iPhone. Rounded edges, square edges, back to rounded edges again...
It's actually a part of planned obsolescence. If they make everything the current fad, people want to upgrade instead. Same with special edition car colors, etc. If you just rotate through some predefined options and make some small subset of those options artificially valuable, the trenders jump on it because they always want to be seen with the latest and greatest thing. It's better than just putting shoddy capacitors in everything at least, so there's at least that.