I think part of this comes down to your definition of "supercomputer", but I mean, pretty much the entire internet is powered by servers. I've never worked there, but I'm assuming that AWS data centers have very powerful computers designed to handle thousands of VMs/containers each, and I suspect with all the AI hype, a large percentage of them have very beefy GPUs in there as well.

If you're talking about the more stereotypical "high performance supercomputers", I think that they are still used very liberally within the defense industry. I think Lockheed Martin, for example, uses them for CFD analysis.