The poster's activities ("studying logic programming", "NLP experiments", "work on Haskell") are the equivalent of painting or composing poetry: a creative activity done for enjoyment. A better analogy for you (not that studying perspective and color theory couldn't be enjoyable in itself even if you don't paint... though of course it's a very different sort of activity from painting) may be "If you paint all day for your own pleasure but never exhibit or sell a picture then what's the point?" (not sure whether you would say that)