Extract (Analysis Tool and Widget) is a function that is allowed on a registered map services in ArcGIS Online (AGO), and helps facilitate Open Data workflows. While you can not extract to a file geodatabase and a few other formats from a map service in AGO, it does allow .CSVs, shapefiles, and a few data types. The same functionality is not afforded in a Federated Portal. Portal requires a feature services with extract and sync enabled per the documentation found here: https://enterprise.arcgis.com/en/portal/11.3/use/extract-data.htm.
A sample of why this functionality would be important is having internal users that use a Portal as their method of accessing GIS data and information to disseminate that GIS stored information to third parties and other internal uses. Basically, it would empower non-technical GIS users to manipulate the data with some guard rails, and not have a massive overhaul of existing workflows by republishing as feature services and breaking links to existing processes.
Otherwise, why have the tools "active" in the map viewer at all if there are no layers that can use that functionality, and allow widgets to activate only to be told that it is an error.
