For the benefit of the sick, orphaned and elderly
The populous regions of your world are heavily industrialised - to the point where the air quality poses a significant health risk to everyone, particularly the sick and elderly.
Sick people are temporarily relocated to health care facilities in clean air regions, and returned home when they have recovered.
Elderly people are permanently relocated to clean air regions. Their contribution to society during their working days is commended and they live out their lives in leisure.
Orphaned people are considered the "property" of the state, and drafted into healthcare and service roles to support the sick and elderly.