If you're building something for developers, you want it to get used. This means your potential users need to find your library, framework, or API. They need to work out whether it's useful for them, learn how to use it, and solve problems they encounter along the way. All these things depend on your developer docs!
Docs aren't just docs: They're your UI, your marketing, and they - not your code - define what your product is.
This talk talk about important functions of your docs that you might not think about, and then some particular pitfalls of documenting things for developers.