> I wonder why that is. My guess is that it's just a symptom of the same thing that causes everyone to stop buying colorful cars, and instead default to a grayscale one: fear that being too outlandish or creative will turn off potential customers/viewers.

One aspect of it is that the sci-fi future is not really a future in general, it's a future how it was imagined at the time. In the 80s we had maximalist fashion - bright colors, shoulder pads, big hair. So the future from that time looked even more so like that.

If we look at the future as imagined in the 40s and 50s we might laugh at the silly looking robots. We'd never put robots like in a current sci-fi movie, unless as a joke. But, at the time they were not made for laughs, people thought that's what robots would really look like.

An even deeper part of this is that the future from 80s from movies that became popular also adds to how we might see the future now. Aethetics from popular movies are immortalized. Like say, you're lamenting why doesn't current sci-fi look like Blade Runner, but imagine if Blade Runner had terrible characters and bad acting. You wouldn't want that aesthetic in sci movies today. It would be associated with crap.