As I understand it, superconductors work best at temperatures approaching absolute zero (-273.15C). For example, Google tells me that the superconductor in an MRI operates at -269C.
There has been a lot a buzz lately about room temperature (25C) superconductors being discovered, but why is room temperature the focus? Why not focus on superconductors that work in reasonably cold environments? For example, we can easily get temperatures to -15C in a freezer. Why not create superconductors that work in that temperature range rather than 25C?
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.