Because with original thinking there is more than one way to do it. Pythonic conformity might make long term maintenance easier, but it's rigidity exacts a cost on expressing new thoughts. R is basically the epitome of Greenspun's 10th rule: it's really their implementation of a common lisp that looks like C with metaprogramming and conditions and restarts and all. They tried standardizing on Common Lisp first (XLisp-Stat) but S from Bell Labs was too popular. In short, today R is a lisp with access to modern numeric libraries.