Members in a program get access to the program when you send out the invitations. Without invitations, the learners, coaches, and facilitators won´t be able to create their accounts in Promote.
So - No invitation = No notifications about what´s going on in the program.
Promote enables you to send one invitation per program and user, regardless of the number of roles (learner, coach, facilitator). A single invitation will trigger a notification for all roles. However, the user only needs to create one account.