... but I believe instead that a lot of people are too lazy to try to use a module than to write their own code.

When I see a module with really poor docs (either too little, or too disorganized, or what have you), the first thing I think is, "Is it really going to be worth it for me to slog through this? Can I reasonably expect that the design and the code is going to be any better than the docs in front of me right now?".

As a general guideline, for better or worse, people use first impressions to save them a lot of time and/or trouble in the long run. A module's docs are my first impression of said module.