Manufacturing Cloud differentiates new business from run-rate business because the two business models require different planning structures.
New or one-time business is appropriately managed through Opportunities, where sales teams qualify and progress potential deals through the sales pipeline. Collaborative Forecasting can then provide sales-management visibility into pipeline expectations.
By contrast, Manufacturing Cloud uses Sales Agreements specifically for recurring or long-term run-rate business. Salesforce defines Sales Agreements as a mechanism to track long-term planned and actual quantities and revenues associated with continuing customer purchasing relationships.
Account forecasting complements this structure by bringing recurring business and other forecast inputs into account-level planning. Salesforce's broader Manufacturing sales architecture emphasizes maintaining visibility into both net-new opportunities and continuing customer agreements so operations teams can obtain a more comprehensive picture of expected demand.
Using Sales Agreements indiscriminately for every new-business pursuit would blur the distinction between pipeline and established recurring demand. Likewise, using Opportunities as the primary mechanism for run-rate commitments omits the time-phased planned-versus-actual structure that Sales Agreements provide.
Study Guide references/topics: Design — New Business versus Run-Rate Business; Opportunities; Sales Agreements; Account Forecasting; Manufacturing Sales Architecture.