This is the only reason (at least for now) that makes me dig into a library code. And I always got some benefit from it.

I think we often treat libraries as voodoo blackboxes, but they're more often thatn not created by normal people with great skills. Sometimes it's a great way to learn a way to code, or even better, to understand the behaviour of a library.

I found myself doing it more often when the IDE itself downloaded and linked the sources. (Lazy, I know).