[silentbicycle]

Oddly, it can also be a downside. A language that makes reinventing the wheel too easy means that people can spend more time saying, "Psh, I could do that in a couple hours" than sharing. Then, when people want to know what the library is to use for parsing HTTP headers (or whatever), everybody and their nephew shows up to suggest their own half-assed framework. It doesn't inspire confidence.

Take that to its logical extent, and ... wait, which Lisp implementation do you use again? Mine only works with SBCL, crap, nevermind.

When somebody has a really thoroughly debugged C library, it can be like huddling everyone together by a fire for warmth in the tundra. If you don't share, man, that's just cruel.