This argument confuses me. It seems equivalent to saying "with mainstream fast food restaurants selling meals with 1600 calories, why are you making yourself a

This argument confuses me. It seems equivalent to saying "with mainstream fast food restaurants selling meals with 1600 calories, why are you making yourself a green salad for lunch?", or saying "with the national debt approaching $35 trillion dollars, why are you shopping around for the best rate on a mortgage?". One answer for all three cases is: I'm not the thing that's big, I'm a different thing that's smaller. Another answer is: if being too large is the problem, then being smaller sounds like a solution. But I guess you're really asking why the developer would spend time on rewriting a library. Is that really surprising? Most of programming is rewriting something that's been made before, either because you have to for your job, or because you need it to do something slightly different, or have different performance characteristics, or just want to learn how it's done.