Earlier quoted context omitted.
It's usually lack of knowledge/understanding and simple inertia, "this is how we've always done it."
I'm afraid you just dismissed the question, not answered it. Plenty of things changed in agriculture in spite of simple inertia. Why does sickle-for-wheat-scythe-for-hay concept seem to prevail for different cultures in distant lands for so long?
But I think that with a proper apparel such as the one we see in the video on the website, the fall can be made gentler while still keeping the significant efficiency gain that the scythe offers over the sickle.