How come we can create sub tasks in the view screen of an Epic (because there is that + button for Child Issues) but the + button doesnt exist on an Initiative view screen so we can create Epics right then and there?
There is no way to add a "+" to your initiatives for child issues. But there are several workarounds:
Epics are a specific issue type that have this create issue in epic feature. It comes with JIRA Software and adds e.g. the ability to filter your backlog by them on a scrum board. Standard issue types - such as initiatives - do not have this feature.
When using JIRA out of the box, you can use issue linking to reproduce similar behaviour. On an issue, under More (...) select 'create and link' issue. When complete, you will see the related epics of your initiative listed on the Initiative's detail view and have a + button available to add more. Note, however, that this does not enable some of the specific additional features of epics.