IEEE Spectrum carries a a nice historical overview of superconductivity by Pradeep Haldar and Pier Abetti who focus on this rather baffling fact:
In the 100 years since superconductivity was discovered, only one widespread application has emerged.
A couple of excerpts:
Since [the discovery of superconductivity by Heike Kamerlingh Onnes in 1911], physicists have sought to understand the quantum-mechanical origins of superconductivity, and engineers have tried to make use of it. While scientific efforts in this area have been rewarded by no fewer than seven Nobel prizes, all commercial applications of superconductivity have pretty much fizzled except one, which came out of the blue: magnetic resonance imaging (MRI).
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Müller and Bednorz's work triggered a flurry of research around the world. And within a year scientists at the University of Alabama at Huntsville and the University of Houston found a similar ceramic compound that showed superconductivity at temperatures they could attain using liquid nitrogen. Before, all superconductors had required liquid helium—an expensive, hard-to-produce substance—for cooling. Liquid nitrogen, however, can be made from air without that much effort. So the new high-temperature superconductors, in principle, threw the door wide open for all sorts of practical uses, or at least they appeared to.
The discovery of high-temperature superconductors sparked tremendous publicity—which in retrospect is easy to see was hype. Newsweek called it a dream come true. The cover of Time magazine showed a futuristic automobile controlled by superconducting circuits. BusinessWeek declared, "Superconductors! More important than the light bulb and the transistor" on its cover. [...]