A few years ago, my team developed a LaTeX editor for iOS, specially for maths teachers who do not know LaTeX. It is still widely used by maths teachers who create content for one of the US publishing houses. Perhaps the problem is not TeX but the editors? No one writes plain PDF or PS, but everyone uses them.
Still the best Sci editor app Iโve ever used was the FrameMaker for NeXTStep. Perhaps we should focus our efforts in this direction?