With the power of Portal in the Cloud (i.e. arcgis.com) it is about time to put the full power of AGS there. There are many places where customers need to do real GeoProcessing and having the ability to take the power of ArcPy and AGS would extend the platform so much further.
Right now; you can do Feature-Layer level functions which happen in the cloud instance of DataStore; but that doesn't touch the capabilities or complexities of real Enterprise Applications.
The flexibility of being able to push layers from ArcCatalog or Pro to a Cloud interface for a eGDB, then have a hosted interface where GeoProcessing scripts/tools could be pushed in a secure/hosted manner to then support the on-demand/surge processes that many need but ArcGIS.com currently can't provide.