I'm totally new to this concept from design perspective. I've worked in past on some of the workflow engines as programmer but never had a clarity on why we chose the work-flow engines in first place. And as programmer I know that there are at least 100 ways to do anything when you are writing code but only few of the ways are the best!

I still don't understand which use cases are best solved by workflow engines (or rather their concept) than designing a good DI enabled application. I'm looking for any general characteristics of domain-neutral use cases, where work-flow engines are one of the the best options.

So my question is: What are general characteristics of a requirement which can be taken as a signal for opting for a good workflow engine and coding around it?

Cheers!