It's possible to overanalyze the outcome but in my opinion, the reason is rather simple: search results. In my programming-related searches, I never saw a result pointing to StackOverflow documentation. Whatever I wanted to know was already answered in a SO question. Take npm documentation for instance, which has covered topics like, "Configuring", "Publishing" npm packages [1].
As much as I loathe the state of documentation of some projects, I'd rarely open a specific website for help - I'll just Google, "publish npm package", "configure npm package", for which, none of the search results point to a StackOverflow documentation page.
As much as I loathe the state of documentation of some projects, I'd rarely open a specific website for help - I'll just Google, "publish npm package", "configure npm package", for which, none of the search results point to a StackOverflow documentation page.
[1]: https://stackoverflow.com/documentation/node.js/482/npm#t=20...