It's a sorry tale of how people can be enticed to make "demo-ware" which looks great when demonstrating something to other people - spinning that desktop cube makes everyone feel like Tom Cruise in "Minority Report", or whatever - and which gets the audience cheering and punching the air at an Apple-style keynote, but which adds relatively little to the experience for most users.
Back in the late 1980s, it really was a usability enhancement to be able to drag a window across a desktop and have the contents actually dragged along with the movement of the mouse, instead of the window outline being dragged and the window then being replotted (which was all the Apple Mac could really do at the time). Back then, opening or resizing a window on a fast system - not a Mac - didn't need a stupid animation of the window outline: it was impressive enough to just have a window appear or resize more or less instantly, instead of having the system stall for time.
What seems to have happened since is that many of the user interface "experts" have unquestioningly perpetuated the rituals of the supposedly most innovative environments. So that means animations of distorted, semi-transparent depictions of windows, complete with wobble effects that even Pixar would be embarrassed to use, ostensibly so that even mundane operations can seem "exciting" to people not actually doing anything more than tinker with their desktop.
I'm not arguing against things looking good, but I don't see anything like the bang for the buck that the introduction of "solid" window manipulation gave us over twenty years ago.