I really dont understand that. The most important point for a sophisticated software like a 3d engine is the quality of their documentations and examples. That is one of the reasons why Unreal-technology sells so well.

And I also dont understand it from the other way around: If you spend several years to produce such a great tool then writing a manual is just a small task but it helps all the world to dive into your genious masterpiece of software so it could even feel good for a developer to write such a documentation. It can be fun and can show the world your concepts and ideas.

But when they lack good tutorials then they do not sell enough copies and they wonder what is wrong with their great tools and abandon to improve it later on.

Documentation is just another part of this software and should meet the same level of support.