There are many scenarios when an app opens user's files, besides interactive Open File dialog. Last file worked on, projects etc. Open/save file dialogs basica

There are many scenarios when an app opens user's files, besides interactive Open File dialog. Last file worked on, projects etc. Open/save file dialogs basically return just file path. Actual file access is a separate API call. Requiring interactivity in all scenarios would hurt UX badly, as UAC story proved.