That's the point, technology has improved over the years and that is what has happened, they haven't been replaced they've simple been able to do more, be more efficient, there haven't been mass sackings of these skilled professionals because of this increased efficiency but rather the service they're able to provide has been improved!
So supposing you automate a large portion of what a radiologist does re: interpreting scans thanks to recent improvements in machine vision whereby a machine can spot cancer better then a human expert, it doesn't necessarily mean you start sacking radiologists but rather you improve their efficiency, more MRIs can be processed by the same person, fewer errors made. Perhaps they can concentrate more on the interventionists side of their profession etc..