Poor documentation practice is pervasive in the free software world. Much of the issue, I believe, is the rise of sites like Stackoverflow. Documentation these days seems to consist of the bare minimum--docs autogenerated from method/function signatures with maybe one or two trivial, useless examples--and an expectation that people will "tinker" with the software and post/find answers on these sites. Google and Stackoverflow, in other words, are the documentation of choice.

I understand: documentation is hard. It's tedious and it's difficult to get right for all the likely/major audiences involved. That's not a good excuse, though. The amount of fad-driven, cargo-cult coding and the like has just exploded in the last few years, much of it essentially copy-pasta from sites like Stackoverflow or whatever a Google search throws up.