It's very irritating to a Python-afficionado like me. Thanks to the BDFL Guido von Rossum, Python has a syntax that is extremely consistent and minimalist, and Guido safeguards this approach through all iterations of the language and its standard libraries. Unlike centrally-controlled Python, R and its various libraries were developed semi-independently by many people working together as a community. Everybody had their own special problems and ways of looking at things, different opinions about which special cases were important enough to break rules, and so on.
Stepping back for a minute, this complexity isn't unique to programming languages. It happens in natural language too, and presumably it happens in the same way. New words and idioms are invented independently and percolate through the community, so that the language becomes a moving target. The difference is that we take this self-regulating chaos for granted in natural languages, whereas people often try to stamp it out in the coding world.
Esperanto is the Python of natural languages. It didn't evolve in a community, or emerge through trial-and-error. It was designed deliberately, and as a result Esperanto is basically free from edge cases, irregularities or unnecessary complexity. I've studied it a little bit, and am consistently impressed by its stark elegance and simplicity.
They say that a camel is a horse designed by committee. Languages are designed by "committees" of thousands of people, who have different axes to grind, and we never even bother to take a vote. And yet this noise gives rise to innovations that no single ringleader could ever have thought up, and beauty that allows for poetry and literature. It's a process of evolution. Perhaps, just like with organisms, chaos and irregularity is the price we must pay for, in the long term, true innovation.