The vast majority of mother - son incest pics on imagefap appear to be of women not really old enough to actually be the mother of the so called son. Or sometimes mother - daughter. The mother just doesn't seem to be old enough. And in cases where the 'mother' is old enough in the pictures, she doesn't appear to be related in the implied manner.

If medical problems were not a serious problem would incest (of age participants) be ok? I guess so. But medical problems remain a serious problem. And communities are also still harsh on the participants, and I suspect also harsh on the offspring of incest couplings. 

If medical problems were fixed then perhaps the societal distaste may go away? Obviously not immediately but it may take a few generations to maybe a millennia or two. Hard to say.

Note: there is no off-spring type medical problems with father son, or even mother daughter incest. Just aversion by society in general.

Medical advances continue to move forward. Eg cloning of human species will technically be possible pretty soon. But cloning is not as fun as actual physical coupling. And physical coupling would still be attractive to some, and still be a problem with advances of cloning. I think the medical advances need to be made in tweaking genes so that off-spring of incest couplings do not suffer. Unfortunately there are more urgent areas for medicine to advance and incest is not one of them. Which government is going to approve of it [ethical nightmare], or fund it? Which corporations or individuals are going to raise their necks and fund the research?

I didn't think so.