Modern data platforms often treat operational systems as legacy constraints to be eliminated. This article argues the opposite. Transactional systems, CRM platforms, and low-latency decision stores exist because some decisions must be made synchronously, locally, and with authority. These “edge systems” are not architectural debt but purpose-built domains of control. A mature data platform does not replace them or centralise authority falsely; it integrates with them honestly, preserving their decisions, context, and evolution over time.