My packages already show up looking like they were dragged behind the truck. I can't imagine what they'd look like if they got fired out of a rail gun.

In real terms, I'm doubtful that the majority of people's goods would withstand that kind of rapid acceleration. Consumer electronics frequently break from hitting the floor, a rail gun would probably shred them. You could accelerate more slowly, but then you need more runway, and you might end up building a skyscraper anyways to get a delivery radius that's more than half a mile.