Video encoding and image compression is a huge use case, and not at all uncommon, so much so that a lot of hardware has dedicated hardware for it. Of course, offloading the SIMD instructions to dedicated hardware accelerators does reduce usage of SIMD instructions, but any time a specific CODEC or algorithm isn't accelerated, then the SIMD instructions are absolutely necessary.

Emulators also use them a lot, often in unintended ways, because they are very flexible. This is partially because the emulator itself can use the flexibility to optimize emulation, but also because hand optimizing with SIMD instruction can significantly improve performance of any application, which is necessary for the low-performance processors common in videogame consoles.