Flet has "Service" components now. Presently they could be added to page.services property only.

If we make a reusable control that would like to use a service, for example FilePicker, we would still need to add that file picker to a page which is wrong from encapsulation perspective (reusable control should not know what's outside).

ServiceHost control will allow to host services used by other controls. It will have only two properties: "services" - collection of Service instances and "content" - control to render as a child.