Have you ever seen when an Imperial Shuttle lands and all the smoke filters out of the bottom?  I was always under the impression that numerous small "engines" covered ships that allowed them to pilot as if they were held by gravity, but in a zero gravity environment.  Otherwise, how would all those ships be able to stay motionless in space?

I always thought it was to add dramatic effect for when vader of the emporer waltz into the scene. My bad.

Futurama: You Can't Prove it Won't Happen

It's just a smokescreen