Part of the problem is, designing a friendly library requires taking into account all of the use cases of other people. Often when you're developing an app, ev

Part of the problem is, designing a friendly library requires taking into account all of the use cases of other people. Often when you're developing an app, even one completely in open source, you aren't designing all parts of it for maximum reusability. There are tons of private APIs in most apps, including most open source apps. It's usually after the application which drove the development of the utility code in the first place is finished and stabilized, that people go back and figure out how to refactor it to make it generally more useful.