Healthcare takes place in many contexts. For small implementations, a single set of patients with a single set of data will suffice; however, as implementations grow in complexity, it's common for them to want to separate there data based on the context – i.e., the care setting. For example, separating active medication lists between inpatient and outpatient settings or having Clinic A and Clinic B sharing the same system but only seeing patients and data for their care setting.
Rather than making the care setting a required parameter of nearly every function in the platform, we would introduce Care Setting as a new properly within the user's context. This would avoid having to change every method in the API to include a parameter for the care setting. It would, however, require us to add "care setting" to many parts of our data model.