Hull shape, warp bubbles, and Star Trek fleet design

Why are Star Trek's human ships streamlined instead of simple blocks?

Their shapes may make warp bubbles easier to project, while Borg cubes favour internal volume and rely on transwarp infrastructure.

Streamlining can matter in Star Trek because a ship's shape may affect the warp bubble it must project. A sphere could be efficient for enclosing volume, although arranging and insulating the interior may be difficult. Starfleet's longer, rounded forms offer a practical compromise between the field shape and usable structure. Borg cubes maximize internal volume, and their established transwarp network could reduce the penalty of an independently inefficient hull.