Some day I intend to write an eloquent essay on the virtues of good software documentation, particularly as it applies to software libraries for use by other programmers. For the moment, I will say only this:
…because the authors didn't bother to write it down.
Choosing to use someone else's code library and API is (or should be) a buy-or-build decision—I choose to use your code because it's more cost-effective than writing my own. So,