tl;dr: Yes we try to document through READMEs, wikis etc. Documentation is hard. not because there aren't enough good tools. there are plenty actually. Problem

tl;dr: Yes we try to document through READMEs, wikis etc. Documentation is hard. not because there aren't enough good tools. there are plenty actually. Problem is: how to keep them updated with frequent changes in code, enhancements, business process changes etc. At very large companies with distributed teams across the globe (I work for these kind of companies), maintaining an updated documentation/readme is the challenge. Do you want to spend the time to update the doc. on every release, every ehnahcement, every production fix, short term/long term projects etc OR you want to deliver the product on tight deadlines. Now once a project is delivered, do you want to go back and updated READMEs ? Wait, I had a piece of code that I delivered in release x.y in New YOrk and wrote a nice README. A developer in London made some changes to it 6 months later but he never updated the documentation on that specific change or perhaps did not know where my README was or perhaps did not care enough. Now my README is outdated and pretty much useless. Very tough.