For a lot of use cases, they need to be viable completely outside of any containment.
If you create a superconductor that needs -30C to function, you can’t use it in consumer electronics because it would make them too large. If you create a superconductor that needs -10C to function, you can’t use it to transmit power over long distances
Don’t get this wrong though, scientists have been working on finding ANY superconductors in the hope of eventually being able to reach the end goal of a room temperature type. There are still unknown mechanisms that cause super conduction, so any breakthrough usually helps us find more possible candidates.