[StreamBright]

We used to use them internally for building a system management application that required talking to databases and an API that nodes could pull information from. This pre-dates system management tools like Chef, Ansible and it was just a tool like that. There is also workflow management tools that (like managing Hadoop jobs for example) that could be written in these. Generally, things where you need to deal with a lots of state (and state changes) from the outside world. I am pretty sure there are other use cases.