First is medical imaging tends to have relatively low resolution and high noise compared to optical images. So there is a danger of over-processing.
Second is, somewhat related, that I think there is distrust in clinical practice and regulation of black boxes where processing happens in the background. You're taking responsibility away from a doctor and putting it on your system, so there is a greater burden of validation.
Third is cultural. Doctors get a ton of training to interpret the signal in these images, and I think there is both a badge of honor in this as well as a barrier to adjust to something new. In my Masters, one of the medical device design instructors talked about a prototype of a digital stethoscope with huge improvements to acoustics. Doctors hated it - even though the sound was better, it wasn't the sounds they were used to. Although this was before the Eko Stethoscope, which is a digital stethoscope and seems to be doing well. Maybe an example of market timing.