Job advertisements for software development roles are increasingly listing contributing to open-source software as a prerequisite for applying. Typically, they ask for a applicant's github profile or equivalent open-source project profile for evaluation.
It seems unfair that programmers level of competence for job roles are partly (or perhaps entirely) determined by their efforts working on open-source projects. It suggests that programmers are supposed to go home after an 8 hour work day and then... continue coding.
Why do some employers require participation in open-source? How should one handle being asked about this if they don't contribute to open source code?