I love the double barrels myself. IIRC, in the first art book for ME1, it was stated that in early development the second barrel was either going to be used as a grenade launcher or for tracer rounds. This however was scrapped in later development but the double barrles themselves remained as an iconic design choice, just like Heimerdinger said.
@Fixers0: An even more accurate comparison would be Somalia, which has no working government. But then, the galaxy doesn't really work like Earth. Even in the terminus, you seem to find a lot of peaceful and productive colonies for whom crime is not an issue and that invite tourism and industry (look at the human colonies that gget attacked in ME2, like Freedom's Progress or Horizon). Since everything is so spread out and maybe not even completely charrted, it might actually make sense to build an out-of-the-way cheap labor weapons factory on some outlying planet, who knows.