Every user in Jira Software can create Scrum and Kanban board in classic projects.
As a Jira admin would be important to restrict users from creating new board with specific permission for it.
Summary
Currently, every licensed user in Jira has the ability of creating a board. They can also opt to share the board or keep it private for themselves.
That can be problematic in scenarios where there are a big number of users from different teams, where Jira admins need more control over the things that are created within the instance. Specially because non-shared boards will not be visible for the admins either.
Suggestion
Create a specific permission that will be required in order to create boards.
seem like Atlassian has the same problem with boards being created constantly
there are tons of "Copy of" boards on their own projects..