I guess reasons to leave steemit may depend on the time spent on the platform. New users may have an information deficit, come with extremely high expectations which won´t be fulfilled afterwards and then leave, for instance. That´s a complete different perspective to the one of an older user that may have developed a certain dissatisfaction during a larger period of time.
When quitting there are always two options: leaving something behind and actively deciding against something (negative experience) or going towards something new (positive experience). It would be nice asking users who stop being active on steemit for their reasons.