There are several problems almost all FE writers have which explain why the documentation can be bad/incomplete:
1) We don't have a lot of time (& what we have is spent programming, or other things),
2) We are always changing things so writing docs is almost a waste of time as it quickly becomes outdated,
3) Things are often hard to put into easy to understand words (at least for me),
4) We don't get paid,
5) We hate writing documentation

I said 'we'...not wanting to tarnish anyone with the same brush as me but that is the way I see it.
With the help of one or two others I hope to get some better docs together at some point after my next proper release...