Not sure about R but I know python is an extremely mathematical language. (Used by A LOT of educational institutions in the UK) I assume R is used for the same reason. So, it would make sense for the computation, it would be stupid to use something like javascript because well it sucks at math.

Bigdata and Bigdata analytics is getting popular day by day. There are a lot more job opportunities for the offshore developers who now Bigdata analytics and crunching. Hadoop is one of the most prominent architectures that is used by the Bigdata developers. Hence, knowledge of Hadoop is also crucial in the industry.