It is possible to attach files during the issue creation screen. Attachment is a field which must be configured to display on the issue creation screen.
Administration >> Issue Fields >> Field Configuration, ensure that the
Attachment field is not hidden.
2. Inspect JIRAs
Screen Schemes and see this article on how Screens are associated with Issue Operations. Once you've identified the screen that's used for Issue Creation, ensure that the
Attachment field is there.