When the first science fiction was written, (and when the first airplanes and dirigibles flew), ships provided the most direct analogs to either the real vessels of the air or the imagined vessels of space. No powered land craft could go in any direction its driver chose; they all required roads of one sort or another (and the largest required roads of iron and could only achieve any size by forming an articulated series of lesser vehicles in trains) It is true that the first tracked vehicles appeared at about the same time as the first dirigibles, but they were in limited use and could hardly have provided terminology that would be easily grasped by people newly introduced to the ideas of air or space “ships.”
With nautical language in place for the hardware, it was no great leap to use maritime, (and then naval), language to describe the operators of that equipment.