It has nothing to do with interoperability on my machine. I use notebooks (and Pandas) all the time, and I consider myself fluent in bith R and Python.
It's because R is a substantial engineering dependency. As I said, our entire stack is Python and Node. Yes, you can call R from Python using Rpy2, but that's a pro-bono project maintained largely by one person. It's great for casual use, but there is far too much risk to start talking about building critical business code around it.
That is true. I actually started my journey with Pandas and then switched to R for the ecco-system and zero based for data science drove me nuts.
But I do feel that the goal is a clone.
"Python has long been great for data munging and preparation, but less so for data analysis and modeling. pandas helps fill this gap, enabling you to carry out your entire data analysis workflow in Python without having to switch to a more domain specific language like R." http://pandas.pydata.org/
It's because R is a substantial engineering dependency. As I said, our entire stack is Python and Node. Yes, you can call R from Python using Rpy2, but that's a pro-bono project maintained largely by one person. It's great for casual use, but there is far too much risk to start talking about building critical business code around it.