Debreasting is not that rare fetish, in fact, it is very popular. even I did that myself on my 3d series receiving quite a lot of requests.
It is just not very common to see any kind of detailed gore on real-life videos or pictures. Even when this kind of stuff gest captured on camera it does not look even remotely as good as drawn pictures of 3d renderings. Drawn pictures look much better than 3d on this topic

Considering how it looks in reality, it is in fact very boring red bloody wound is she is alive and very clean yellow fat if she is dead. you can check it by googling "Woman Breast Cut Off" also women look quite ugly without proper makeup.

So we do not realy want it to be realistic.