Do all ERP systems cater to the need of all departments of an organization?
Different companies have different ERP requirements therefore there are many ways to implement a solution. But collectively the term ERP refers to large applications that replace a multitude of independent applications or legacy system of an organization which caters to the need of all departments.
Some companies limit the scope of their ERP software to a few vital applications that will help them streamline processes or make information more easily available. A company that wanted to just integrate accounting and finance with payroll, for example, also could use an ERP solution.
In such cases, organizations might prefer to use ERP to integrate certain systems and leave legacy systems in place that are better able to handle specific tasks.