monotremata

In addition to “format shifting,” which is a well-recognized use case, and game preservation, which is a huge and under-recognized public interest in emulator development, emulators are also used for the development of homebrew software. E.g., there’s a port of Moonlight for the Switch, which lets you play Steam games streamed from a PC using your Switch, letting it serve many of the purposes of a Steam Deck. That’s huge! It would be way less practical to develop this kind of software if you could only test on real hardware. Testing on real hardware is also essential, of course, but testing on an emulator is vastly faster for rapid iteration.

It’s also used for sending huge amounts of data long distances. “Never underestimate the bandwidth of a station wagon full of tapes hurtling down the highway.” That’s usually attributed to Andrew S. Tanenbaum, but wikipedia follows that with “other alleged speakers include…” so take that with a grain of salt. They do note that the first problem in his book on computer networks asks students to calculate the throughput of a Saint Bernard carrying floppy disks.