[mvonballmo]

Documentation for internal consumption often makes assumptions that no longer hold outside of the company. It might reference internal machines or drives that will not be available. It might take shortcuts that will be confusing enough that it will be worse than having no documentation at all. It might just be a few bullet points that refer to asking the right person internally.

If you've ever taken over a department at a company, and inherited the documentation, you've experienced this. It's sometimes better to just reverse-engineer the current state of things than to try to use outdated or misleading or very sparse documentation. Documenting the current state cleanly takes time, effort, and capability. It's an ongoing effort that requires budget and capacity.

And, most of all, it requires that the company see the need of having a good knowledge base, despite such a thing being a short-term cost that only pays out in the long term, and then, in ways that you won't be able to ascribe to one department's budget or another. Corporate structures can get in the way of cross-cutting/long-term benefits.