A lot of it is driven by media (movies, games), and falling back to a known style is easier than coming up with something new, which reinforces the style. Whereas if someone comes up with a new flavor, it might not even read to the audience as "futuristic", even if more thought went into it. And coming up with something that's not just a skin on tranditional designs is really hard!

could one argue AR designs should be considered more futuristic?

Fake movie UI also is not driven by the same concerns as real-world UI. It's usually much more a flashy center-piece and then just stuff around it that doesn't need to mean anything, because it's not actually intended to be read like a real UI is.