Actually aside from "Rule of Cool", there are two very important artistic reasons: Visual identification and creative direction. Hecate is certainly not utilitarian design, but she is hella memorable by her unique design. As for creative direction: There are several different schools of asset design. Some designers want realism, focus on technical aspects etc. so their ships will look believable as space warships, but design in this case is secondary. FS is actually very close to second pole of this scale, and it's: creativity. FS is almost completely focused on unique style of warships and artistic aspect of asset design.
It is a matter of taste and general direction of overall mood of the game. FS is certainly not focused on realism in general, both in physics, lore and visual aspect. For this reason, I don't feel an urgent need to justify the "elephant ears" of Hecate or other non-utilitarian elements, because they all contribute to the design and artistic direction in general. For the same reason, smoothness or blockyness of ships is completely irrelevant, but overanalyzing is not always a bad thing :].