The Force is what makes Star Wars universe unique and the people that can destroy small armies and control minds should justifiably have a big part in the galaxy. It's not like there aren't books dealing with the non-Force users (the Han and Lando trilogies, the Tales series, Fett novels, Clone soldiers novels, and the X-Wing series not to mention most of the 'Force user books' have plenty of plot points and subplots dealing with things happening elsewhere to non-Force users).