Semiconductors are used for transistors because they give us the ability to electrically control whether they conduct or resist electrical current. I don't know what mechanism you'd use to do that with superconductors. I agree you don't 'have' to have resistance in order to achieve this functionality, but at this time semiconductors or mechanical relays are the only ways we have to do that. My focus is not in semiconductor / IC design either so I may by way off base, but I don't know of a mechanism that would allow superconductors to function as transistors (or "electrically controlled electrical connections"), but I really hope I'm wrong!