Service Portal Administration has three main sections: General, Services, and Categories. It will seem, as you work through these sections, that some settings are duplicated between General and individual Services. This is because Service Portal leverages several components to enable a never drop/never fail philosphy.
Never drop/never fail means that things don't get stuck in the ether, hung up forever. They don't get stuck waiting for a technical resource that may have other priorities or be on vacation to get to the error. Processes all have defined fallback and error processes that are as robust as possible.
Part of this never drop/never fail functionality for Service Portal are a series of attributes needed for form functionality that are defined at the Service, Kapp, and Space level. This means that if the settings are not defined on the Service, they fall back to the Kapp settings. If the settings are not defined on the Kapp, they fall back to the Space settings.
This allows for items like assignee group to have a default, so no task will fail because the assignee group wasn't specified (or was empty). The task would go to the default group to be processed instead.
Note that these attributes are all built to the support the preconfigured default process itself, which is as follows:
1 optional approval
1 task/work order
Other workflows may be built and used, but they may or may not use the provided (or new) attributes. This would need to be decided/done at build time of these new processes.