I'm not angered, I'm more wondering about the usefulness of the arbitrary line you've drawn in the sand, and even the shape of the line.
RShiney lets you build interactive webpages with advanced GUIs; if <webdev stack> counts as a programming language, why not R?
Many people like python because it lets you script things, and you can even make your script executable with a shebang at the start (!# /bin/python) -- and while true, that isn't built into R, you can run R scripts programatically (> Rscript myfile.R), or make this executable by putting it in a standard shell script.
I approached it like you described. I wouldn't want to do a really complex REST API in it, but as a wrapper for calculations, we've got a repeatable pattern to run them in a cost effective manner.