For historical context, R was not initially intended to be a standalone scripting language runnable via POSIX conventions and didn’t gain these features until c

For historical context, R was not initially intended to be a standalone scripting language runnable via POSIX conventions and didn’t gain these features until circa 2010. R is designed to be used interactively, like the S language it was based on, a style later made familiar to students via MATLAB and TI graphing calculators. Before Rscript it was common to hack together shell scripts that cope with the expectation of human TTY input to run R in production, which functioned well as a “you must be this tall to ride” sign for people who might not appreciate how unreliable R code can be compared to a traditional language.