It would be nice to be able to publish geoprocessing services to ArcGIS Online in the same way you can publish them to Server. Not everyone has a on-premise solution, but many do have access to AGO. Also, depending on the situation, utilizing the cloud to host these geoprocessing services can be preferable to an on-premise solution. Hosted geoprocessing services could use credits in the same way other published content does. I'm surprised with how far AGO has come this isn't a capability yet.