> I thought the point of native command queuing was precisely to enable the drive itself to make these lower-level scheduling decisions
The main purpose of NCQ (and SCSI command queuing which came way before it) was to allow higher levels of parallelism at the drive interface. This does allow the drive to do some smart scheduling, but still only within that fairly small queue depth. Scheduling across larger numbers of requests, with more complicated constraints on ordering, deadlines, etc., remains the OS's job. And once it's doing that, the incremental benefit of those on-disk scheduling smarts becomes pretty small.
The main purpose of NCQ (and SCSI command queuing which came way before it) was to allow higher levels of parallelism at the drive interface. This does allow the drive to do some smart scheduling, but still only within that fairly small queue depth. Scheduling across larger numbers of requests, with more complicated constraints on ordering, deadlines, etc., remains the OS's job. And once it's doing that, the incremental benefit of those on-disk scheduling smarts becomes pretty small.