You see, back in the ol' stagecoach days, the fella that wasn't steerin them hosses sat up front with the driver and kept a lookout for suckas what that might try and rob said stagecoach - and the shotgun? Well, that, my friend, was his theft deterant. Nothin like two barrels o' buckshot to keep punk suckas off yer back.
So, clearly, aside from the actual driver's seat, shotgun is the best darn seat in the house. Yeah, it was cool when you were a kid riding the schoolbus to sit waaaaay in the back. But once you get access to some real wheels? If you ain't drivin, you want to be ridin shotgun.