A common well-being issue in open-source communities is the tendency of people to over-commit. Many contributors care deeply, at the risk of saying yes too often harming their well-being. Open-source communities are especially at risk, because many contributors work next to a full-time job.
The contribution graph and the statistics on it, prominent on everyone’s profile, basically rewards people for doing work on as many different days as possible, generally making more contributions, and making contributions on multiple days in a row without a break.