[aflag]

Fair point, but I really doubt that is really a key component, specially given how fruitfull the developer market is. Very few people stays in the same company for more than 3-4 years in my experience. So, if you're just going to stay a couple years, you probably don't care about your replacement value.

I'd say that, in general, people don't like writing docs or answering to people. But if someone asks you a question, it'd be very hard to decline to answer, whereas writing documentation takes effort and initiative (and it won't prevent people from asking things, because most people don't like reading docs). Unless there's someone pressing for people to do it, they simply won't. Both because they don't care about doing it and also because the activity is not valued anyway (ask any project owner if they'd rather have great documentation or one more feature).

Also, the value of documentation is questionable in the simple software using standard components as most of us do. I'd be interested in seeing a study to know whether good software docs really improve productivity or reduce the number of bugs.

[pydry]

You're right - I think a lot of people don't care.

However even if you take out the replaceability I still think that there's a relatively limited upside.

Thus you're left with conscience or a sense of professional pride as motivators to write docs.

[aflag]

Yeah, there are no incentives. No one will praise you for writing them, they will probably not be well maintained and other people will make changes and not update them. People will still ask you privately instead of reading the docs and will get annoyed if you tell them to read the docs. You yourself will likely not really refer to them anyway, as you probably already have them memorized for the 3 year period when they are relevant to you.

[thu2111]

Isn't stackoverflow a rather good demonstration of the point? People like answering questions so much they'll do it for free. There is no SO of documentation.