Exactly. These fictional UIs are designed for a single end - to look good on camera. I think there is an inverse correlation between "cool" and "useful" - the "cool" often distracts from the "useful". While this kind of UI could work for something trivial like a simple calculator or alarm clock, in my experience it does not work for serious applications. As works of art however, these things are a beauty to look at - http://sciencefictioninterfaces.tumblr.com/

I had this idea first back when I saw Star Trek The Next Generation and its slick flat computer panels, called "okudagrams" after their designer, Michael Okuda - https://en.wikipedia.org/wiki/LCARS. I tried to reproduce the look in a note-taking application. It didn't work. The UI was dominated by these large colored buttons and arches, with too much contrast against the black background, leaving too little room for the actual content.