Why use R? Because that is what the professionals use!
The moral of the story is not that one should blindly use professionals’ tools; that can be just as bad as ignoring them. You don’t need to use Google or Facebook’s infrastructure to run your personal blog, just as developers shouldn’t employ the GPL simply because it’s the same license Linux or MySQL uses. But if you want a no-bullshit take on which technologies actually deliver, you could do a lot worse than watching what the professionals use.