Because that's what the public is buying, especially these days. The movie and TV definition of "science fiction" is very different from the literary definition. You can pick up a copy of Analog
and find an intriguing SF story on the premise of whether or not a genetically engineered pig would be kosher-- but a movie or TV show must have Explosions! Space battles! Ray guns! Retarded characters! And, of course, sets that look like factory basements and costumes that look like leather bondage gear. That's why Posthuman
is such a breath of fresh air.