Wahey! April 1st comes early!
1. The library/code is good, but doesn't quite work the way I want it to
2. The library/code is close, but getting it to work the way I want is painful
3. The library/code is bad
4. The documentation is bad/nonexistent
5. The license is prohibitive or annoying (i.e. it's not LGPL or BSD or the like)
6. I enjoy writing code and sometimes I feel I could do it more elegantly, or efficiently (I might just want a very specific and optimized part of it)
More often than than not though I just enjoy coding and I love learning to code by writing new code. The black box thing... eh... I like to tinker under the hood and find out how things work.
But my point is that finding code is not that hard. It's finding code that fits *exactly* what we want. Code is usually just not quite as modular as we'd like to believe and, if we're honest, as programmers we have a certain vanity about writing code so it does things My Way.