Everyone who doesn't tightly control the systems they deploy to. io_uring is a new and developing interface so to support extant systems running libraries need

Everyone who doesn't tightly control the systems they deploy to. io_uring is a new and developing interface so to support extant systems running libraries need to have fallback codepaths. Or more likely: they already have existing codepaths for the previous interfaces and add io_uring as a faster alternative.