I think after you write a manual for your first few projects and clearly less than 1% of your users read it, it gets hard to motivate yourself to write another manual.
The advantage of documentation isn't that users read it before asking questions.
It's that you answer questions by pointing at the relevant section of the docs.
If that section doesn't exist, it's a good practice to see that it does (either write it yourself, have another contributor write it, or encourage the person asking the question to submit a doc).
