To piggyback off what @Alexis said, one of Asana’s most powerful use cases is the “work request” workflow.
A few of my clients use Asana as a IT Request flow as well as a design request flow. In these cases, project members need to be notified when a new request hits the project to ensure that a request does not fall through the cracks.
Given the customer feedback, we have added a box to enable/disable task creation emails when inviting new members to a project.