Why do you need special rules software if most packaged systems and BPM/Workflow software have rules abilities built in?

Well frankly every programming language that has ever included an IF-THEN kind of syntax allows rules at some level. It’s a question of how easy it is to work with the rules, make changes, share them for centralized decision making, and so on.

Some kinds of rules are closely tied to the package software and are only changed in context with that software. They might as well stay in the vendor’s offering. So a workflow system might have the ability to control rules like: “If the approval is in the reviewer’s inbox for more than three days, display an alert message.” It’s clear, simple, and tightly tied to the context. But what if the same workflow software has a rule that says: “If the customer policy application is approved, send it to billing”? The rules involved in approving or declining an application could be massive, subject to frequent change, and shared by other systems who need the same decision process. These make sense to separate from the workflow package and manage as an enterprise asset. That's where business rules come in.