Why does software documentation stinks? I think companies are afraid to produce good documentation because it makes them accountable. Your documentation says the product should do XYZ but it only does XY.
Documentation is time consuming. It requires accuracy and correctness.
I have bought a few products that advertised XYZ. However, the software only delivered YZ. That's good software. I have bought some products that does ABC which is not quite the same as XYZ.
The names have been changed to protect the guilty because I can't prove it. Their documentation stinks!