the biggest concern I have heard from friends who work in stats and mathematics academia is that it is much, MUCH easier to publish a package in CRAN than to PyPi.
I think most users of Python are that... "users". But R is used by creators of algorithms who find it very easy to create and distribute code.
In fact a lot of them talk about how difficult it is to install packages in python, while any R script has "install.packages" right in it.
I'm willing to bet if Pandas/Numpy/Jupyter built a CRAN-PY and made the packaging system similar to R, the adoption would be much different.