I consider one of the most important part of any project - is its documentation. I worked in many companies before and if I have to recall one single thing they all had in common - it was lack of documentation.
Let me be here more specific - it is not just presence of written documentation, because many companies do document their work, but it is it is also documentation quality. Documentation must be well organized, updated as code evolves and above all - not misleading.
No, it is not only IT companies - it is a common problem of any technical project. But I will limit my article context only about IT - because this is my comfort zone.
If an issue is not documented, then persons lose time to understand it, if they don't understand it, they will extend it using wrong assumption which will lead to bugs which will cost money. If it is written down, but statements are confusing - this will lead to misunderstandings which results in additional problems and costs.
Long story short - I am very sensitive to documentation problem. This is why I spend a lot of time updating Papermerge's documentation.