I also didn't realize it could be used for all syscalls, but storage access and networking seem to be the biggest use case for it.

Depending on the exact setup, storage IOPS can be increased by up to 100% versus the older asynchronous IO kernel API [1], only beaten by pure user-space implementations that aren't as feature-complete.

[1]: https://dl.acm.org/doi/pdf/10.1145/3578353.3589545

That could be because there's not another reliable way to do async reads and writes to disk files?