There are many, many features built into SCSI that are not used. Disk to disk copying and mirroring without host intervention. Command list sequencing between multiple devices to get the devices to carry out the work without host intervention. Multiple device classes (block, serial, CPU, Co-pro, sink, scanner, all sorts). Multi-Master operation. Host to host rapid data transfer (remember IP over SCSI? pre-dated gigabit and was DAMN fast over optical). File system support primitives for device locking down to single-sector operations. Multiple overlapping access requests queued by the target device itself, calling back to the initiating device (a host, or even another device).

The concept of a "Host" on SCSI never really existed, it was always Initiator and Target, and this means that any device, not just computer host adaptors, could initiate control actions on any other, in any order, at any time. Wonderful system.

If you haven't guessed yet, I was seriously into SCSI at one time