The insulation keeps the heat inside the box, and putting the snake in the bag keeps it secured away from everything else. Most of the snakes I've had shipped usually have crumpled up newspaper in there too, so the snake doesn't get thrown around in transit.

Some people pick up their snakes directly at their hub (airport), you'd have to call to find out which hub it'd be coming in. I have gotten all of mine shipped to my door with no issues, but it all comes down to who you purchased it from. I've seen some bad unboxing videos where the snake didn't make it, it's usually the shippers fault