No, just design aesthetics. Space craft are supposed to look sleek and fast. Not that it matters.
A pile of sandbags held together with chickenwire won't do? I understand the HMS Titanic looked pretty good setting out on its maiden voyage. Just wait till we have an interstellar ship going an appreciable fraction of the speed of light. Would it not be somewhat comforting to have a bumper made out of a couple good-sized asteroids out front? Just in case you come across a hydrogen atom out there; don't want a chip in the windshield. Can't comment on what lack of various environmental factors such as the magnetic field we're all used to might do. Guess there is one way to find out.