Yeah, but what if you want to use 6 devices and a scanner?
They don't just sell SCSI towers in computer shops these days and the wiring is complex to interface to the SCSI-IV.
The more connectors there are the more RF is reflected so it needs to be kept short, simple and high quality.
IDC connectors at least 10cm apart, for SCSI-2 you need a chain no longer than 2/3m including the scanner cable. IT needs to be active terminated with termination power.
And to go from SCSI-IV to tower to scanner to terminator without putting a wadload of adaptors in between would need a custom built cable.
Cables built to customer spec would be great...