Each of these systems has its own databases and seldom passes information to other systems in a timely manner. SAP takes a different approach. All applications access common data. Real events in the business initiate transactions. Accounting is done automatically by events in sales and production.
Sales can see when products can be delivered.
Production schedules are driven by sales. The whole system is designed to be real-time and not historical. A company implementing SAP adapts its operations to it to achieve its efficiencies and power.