SCSI-connected (flatbed) scanners existed a lot in the 90s and early 2000. Usually, they did need a vendor or vendor-specific (TWAIN, sane...) device driver to work, and IIRC usually implemented the 03h (PROCESSOR) device type.
Why was the device type and command set from the SCSI specification meant for such devices not used in many popular devices, and did any mass market scanners implement it at all?