Steering is no problem; in space everything rotates about the center of gravity, regardless of shape. You probably would have boxy starships for the same reas

Steering is no problem; in space everything rotates about the center of gravity, regardless of shape. You probably would have boxy starships for the same reason you have boxy houses: more usable space. The same arguments apply for spherish houses, but those never caught on. Given the distance that the starship is going to travel, the main cost is probably not the materials so much as the time, so you'd want to maximize the amount of stuff you could ship back and forth.