in the case of a portChannel as an L3 entity, it allows for the added capacity/redundancy of the link as well as provides the layer 3 topology either wanted or in some instances, required, such as when you need to make a multilink connection to a router from your switch.
or perhaps you have a routed core infrastructure created in your L3 environment and you wish to increase the capacity of the links between devices without using VTP/trunking.
