Or why can't a trained Imperial Storm Trooper seem to hit the broad side of a planet?!
The humor website Cracked recently published an article that makes this actually more plausible than it seems. Here's the science:
All throughout the Star Wars trilogy (yes, we're calling it a trilogy, and always will) the enemy Stormtroopers spend almost every battle firing wildly, missing slow-moving targets, and are generally unable to land a shot roughly in the same zipcode as the good guys. But we know they're not incompetent: We see their handiwork elsewhere in the movies -- like when our heroes stumble across a destroyed sandcrawler -- and Obi-Wan Kenobi himself even says: "These blast-points... Only Imperial Stormtroopers are so precise." These are supposedly squads of cold, calculating, efficient murder machines, professional soldiers literally bred for the purpose.
And may the Force be with you always!