a) Because I stare at a computer screen ~10 hours a day at work. When I am reading in the evening I prefer to have a book, which I can underline and scribble in. b) Every programmer over time develops tiny helpful apps that make life bearable, having to rewrite all those apps / utilities in a fresh new language is a burden that I would like to avoid. c) Admittedly I am a bit more aggrieved than most people because my languages of choice are lisp, scheme and python.