There's a virtuous circle with documentation: if you start with something that's complete and correct, then when you make a change which is visible to the code'

There's a virtuous circle with documentation: if you start with something that's complete and correct, then when you make a change which is visible to the code's clients you can go and change the documentation in the same patch series, and check that this happens as part of the main code review. Digging yourself out of the hole where your documentation is already wrong or incomplete is much harder: when you go to describe a change you might find that the thing you're changing isn't mentioned, or is described wrongly, or there is no terminology for the thing you need to talk about. So you need everyone to take care that standards don't slip, which is why it's important to make the importance of documentation part of the company culture, and make sure every programmer is capable of doing their bit.