Why can't the submit button appear on the last tab only?

Good Grants allows applicants to complete their application in any order they like after completing the required first tab wherein a category is selected and an application name is assigned. In keeping with this principle, a user can also submit their application from any tab, provided their application is complete. While it's not possible to restrict submission to the last tab only, applicants will still need to complete all the information before they can successfully submit their application.