Face it, most people wouldn't be interested in watching a movie about astronauts walking around on Mars systematically looking for interesting rocks and signs of life. The way the producers see it, the movie needs a hook to catch and hold the audience's attention. Realism, smealism. Give the audience alien artifacts, explosions with sound in a vacuum, and a love interest complete with OSS (obligatory sex scene). Most movie makers couldn't care less about realism. All they care about is butts in seats and follow-on video/DVD sales. That explains the dreck we see in space movies (and most others) with the very notable exceptions of "2001" and "Apollo 13". It also explains how movies like "Titanic" and "Pearl Harbor" end up they way they were.