Why did they determine to use the Enterprise Resource Planning (ERP) system instead of manually working?

Suppose there is a company that does all the work manually and has a particular system in each department. After spending a period of time, they wanted to automate all the company’s functions and operations, and they decided to apply the Enterprise Resource Planning (ERP) system to their organization. Why did they determine to use the Enterprise Resource Planning (ERP) system instead of manually working?