Why not? Every science/statistics/math/finance/economics person I know uses R. Lots of slightly more 'casual' users, but it's gone completely mainstream. Universities around here have it installed on most lab computers.
I'm also pleased to see Fortran is still going strong. Great language for crunching numbers.
R may be niche as a programming language, but it's mainstream as a tool. It's a language used by many, many amateur and non-programmers. There are more people out there that have data to process than there are programmers.