So if documentation indeed speeds you in the long run, why is documentation not getting the proper attention? Is this because people are lazy? It can not be, the same team produces good quality code, code with low defect, high code coverage, good performance, not many security issues. So why is documentation not good?
Because the quality of code is maintained due to a process put in place. No developer makes changes to code and sends it straight to production. Change goes through a review process. Someone reviews the code. The entire set of test suites is executed on the modified code. In some teams code even goes through manual testing, user acceptance testing by QA team, or product managers themselves.
Trying to keep any of the code hygiene metrics up without this review process would be difficult. Without such a process, expecting documentation to stay up to date, give accurate/reliable information about how the product works, the internals etc, is just too difficult. Some documentation champions will come, sure, they may keep the documentation up to date for a while too. But in the absence of constant maintenance, the documentation will slowly start going out of sync. And once the documentation is out of sync, the urgency to keep it up to date starts going down because if documentation is not up to date, people will not be able to make decisions based on the documentation, and will have to rely on talking to each other, or resorting to other means like trying it out on live product etc, and if people are doing that, then why bother updating documentation?
Continuous documentation is that process. Just like continuous integration, where you do not allow a change to go ahead unless the tests are passing, continuous documentation does not allow change to go ahead till documentation has been written and approved.