Subscriptions should be designed in reference to good practice. One good practice for enterprise-level companies is to design subscriptions based on tiers. One important reason for design Azure Stack subscriptions in tiers is the possibility to scale the Azure Stack services based on your needs. During the deployment, the default subscription provider is being created. This one should be used to manage Azure Stack, deploy resource providers, and create tenant offers and plans. It should not be used to run customer workloads and applications.
As Azure Stack can be designed in an Azure-connected scenario and a disconnected one, the subscription design management has to rely on that model.