When 3D acceleration became mainstream and people started developing 3D-accelerated desktop it was very trendy to have a bunch of pointless 3D stuff going on. I think it was around that time that compiz and its 3D burning cubes and other mostly (but not entirely) useless eye candy were released: https://www.youtube.com/watch?v=4QokOwvPxrE

I think there were two reasons for this:

- It looked cool, even if sometimes very impractical. Now it's a bit mundane but at the time it was like breaking the 3rd wall, we were so used to the flatness of the desktop that it was really weird to view it as a 3D object.

- Apple and Microsoft were in no rush to bring these features to their commercial OSs (and proably for good reasons, MS tried to have the 3D carousel in Vista but even that wasn't very useful). That meant that people in the Linux world in particular could show off "hey, can your Windows XP do that?"

But of course eventually we realized that 90% of these features were counter-productive so we only kept the bits that made sense (ability to scale down windows in real time easily to make thumbnails or previews, faster rendering, a bit of transparency etc...).