I cannot speak to R, but the Emacs learning curve is the primary reason org-mode is not more popular. There may be a break-even point past which learning Emacs is a net benefit, but few people have the time, skill, and inclination to reach that point.
It is a good thing, that slowly other editors gain support for org files. I've seen them at least highlighted in VS code recently, when someone else shared their screen, even if that is but a tiny fraction of what support for org files can mean.
