is the primary drive for the borg perfection and efficiency? if so, why do they leave themselves looking like a 5th grade science project? i mean with all that tech, including nano tech, it is much better for them not to look the way they do. it would probably make them less vulnerable as they would be more agile and have less things people can get their hands on and rip off.
just a thought.
The Borg were intended to personify the fear of rapidly advancing technology in some people. As such, it is entirely appropriate for them to look like cybernetic monstrosities.