The thing is, when you have 4 radiologists reading 100 scans each, if flagging and highlighting and generally improving performance of these personnel leads to two of them being able to process 200 scans each, the other two are out of a job.
They have been, de facto, replaced by computers, even if the job role still exists.
It's easier to see this if you break down the work not into images but into human-image-minutes. If there are 100 minutes of work, but you can assign the computer 50 of them which it can complete in seconds, the same number of human-image-minutes can be completed as before, but the computer has now taken them away from a human.