A big problem with R is that it's just stats. The other day I wanted to do a simple loan amortization (simple PMT/IPMT in Excel). People say 'use R over Excel!'. Right. There are some clunky barely-working packages in R that do half of what you need and some stack overflow posts that mostly show how to do the other half, but that's no basis to build on.

And don't get me started on string handling in R, or that there's no way to get the path of the currently running script, or a dozen other things that are trivial in a general purpose language but are a major pain in R. R is not 'general purpose' enough, and it doesn't have to be useful to write both kernel drivers and database REST frontends, but being able to do things that are math-related and not purely stats - that's not too much to ask for I'd say. Especially because it's not reasonable to ask people whose main job is not writing software to learn multiple languages/tools.

(Other recent example I remember: how unintuitive I found it to plot a sine wave and its first and second derivative. My Mathematica-oriented colleague did it in 2 minutes.)