The Berkeley Institute for Data Science hosts research, events, and tool development focused on facilitating data-intensive research. Today, computational research and data analytics relies on complex ecosystems of open source software (OSS) tools and libraries. Software documentation is crucial to help researchers discover and use these tools, to help build a community ecosystem of data science packages, and to define best practices in the field. However, software documentation in open source is notoriously considered low-quality. Why is good documentation so difficult to write in open source software, what can communities do to better support good documentation in their projects?