Output nodes are necessary to carry the information that is available within a stream at any point to the outside, for example to inform a user or administrator, or simply to write the information in the stream to a file. Information present in the stream can be any static or any variable information.
If you want to inform a certain person about the progress of the export during an export, it is possible to write an email to the person concerned. This can be done after each node. It is also conceivable to write all information about each individual processed asset to a file during an import in order to evaluate this information in a later step.