Initiatives can currently be created in one product line and be used across many different products and product lines. Goals cannot even though they are a natural extension of this concept.
In my use case I have initiatives and goals that are fulfilled by many disparate products and activities but to achieve the desired functionality, I have to restructure my product hierarchy or have duplicate goals.
PMM and PM team both have features/activities that share a common goal for a product. Goal exists in the product workspace, but PMM can't link activities to it from their workspace. Goal is not relevant for the entire company, which is the shared parent product line. Workaround is to use initiatives for what should be goals, or create an extra level in the hierarchy simply to support this workflow.