The original Airpods Max (and presumably these) had a 'case' that only covered the earmuffs and not the band. Some people called it a 'diaper' due to its appear

The original Airpods Max (and presumably these) had a 'case' that only covered the earmuffs and not the band. Some people called it a 'diaper' due to its appearance. By default, at least the earlier firmware revisions (don't know if this got changed), the headphones would stay on unless they were put into their case and it would kill the battery.