No one uses R for it's amazing language*. The language sucks. R is used because it has nearly limitless, tested, and approved statistical algorithms. Want partial least squares, support vector machines, linear models, principle components analysis, Fisher's exact test?, they are all there waiting to process your data. Along with hundreds of other analyses that you might really need to use but don't even know about yet.
"Python" doesn't have this stuff because it is a language, not a set of statistical methods.
*there may be a few deviants who use it for self flagellation