Why are subtasks restricted to some issue types?

[Benjamin Peikes]

We're trying to use JIRA for business processes. We set up a workflow for a business process, which will also include a bunch of subtasks. Some of these subtasks have their own workflows, but it appears you can only add a subtask using the Sub-task issue type.

Why can't Sub-tasks of an issue be of any issue type?

[Nic Brough -Adaptavist- · Accepted solution]

You can create subtasks of any type.  You can add bug, feature, whatever as a sub-task type.   What you can't do is re-use parent-types as sub-tasks.  It's a structural thing, as the type determines whether it can contain other issues, or it belongs to a parent.

[Joe Pitt]

It is how the product is designed in the code. Simple as that.