Dataflows would be really useful if you could connect to them via DirectQuery. This would mean that we could query enormous dataflows that are not practical to load to the Data model and can make agg...
The reality is that there are two classes of Power BI users. There are software engineers / data experts that typically own the data sources that feed Power BI. These people have the expertise to write complex queries and do other calculations against the source data. You need to give these people a way to put data from their source into the service efficiently to be used by the other type of user. These people NEVER want to pull the same data from their source more than once for obvious reasons. The other user is the business analyst. This person typically does not have a background in SQL or programming. They need to be able to use the graphical interface to efficiently transform the raw data that has already been brought into PowerBI by the data source owner. You can't expect the data source owner to do all the aggregation / filtering / etc against the data before bringing it into Power BI service. It would seem to be the whole reason for Power BI is to enable people who don't have backgrounds in software engineering / SQL to analyze the data.
