Before software can be reusable it first has to be usable.
Reusing pieces of code is liked picking off sentences from other people's stories and trying to make a magazine article.
I've finally learned what “upward compatible” means. It means we get to keep all our old mistakes.
Telling a programmer there's already a library to do X is like telling a songwriter there's already a song about love.
It can be better to copy a little code than to pull in a big library for one function. Dependency hygiene trumps code reuse.