I think of K like a super-geeky version of Excel, for people who do quant stuff. People do very useful, cryptic stuff in convoluted, bespoke Excel sheets, updated and grown over decades with 37 variants of almost-but-not-quite the same VB function, etc. I imagine the K world is very similar, except K users can meet in London pubs and trade little snippets of K handwritten on scraps of paper between them like Pokemon cards.