The first time I saw Angry Red Planet was when I realized that the science fiction films of the 1970s were the first to consistently have orchestral scores. For most science fiction before that, the pop music of the day often served as inspiration, and four-piece house bands the execution of science fiction music. There are exceptions, of course, but not many.
No, that's hardly true -- I don't know why you'd believe that. There were plenty of SF movies with orchestral scores in earlier decades. The Day the Earth Stood Still, This Island Earth, The War of the Worlds, The Time Machine, pretty much any Ray Harryhausen movie, Fantastic Voyage, 20,000 Leagues Under the Sea, The Creature from the Black Lagoon and its sequels, even most of the low-budget films of Roger Corman or Bert I. Gordon. The exceptions were the films that didn't have original orchestral scores, like Forbidden Planet with its "electronic tonalities" or 2001 with its reliance on stock music. There were a number of great composers doing orchestral scores for genre movies back then, like Bernard Herrmann and Miklos Rozsa. As well as composers who did orchestral scores for lots of B movies, like Herman Stein, Hans J. Salter, and Albert Glasser. Yes, there were some movies that had jazz scores or pop scores later on, but there were many traditional orchestral scores alongside them, even if the orchestras were sometimes fairly small. (Which wasn't a bad thing. Herrmann's classic Psycho score was done entirely with strings.)