They're comfortable, for one thing! (If you're River Tam.) And interesting. And sometimes you find candy. And they provide a fun change of perspective.
When Simon steps onto the nearly-repaired Firefly in the Milliways garage, he's carrying a heavy brown paper bag; the contents jostle against each other with the flat click of plastic.
He sets the bag down just outside the engine room, and taps with his knuckles on its open door.