Scenario: You have published a Power BI Desktop file with a report to Power BI Service. You want to give certain users access to some pages in the report. This is not a security mechanism although it could be, if you want to control security at the report layer.
Solution: When a customer asked about this scenario, my first thought was to create reports directly in Power BI Service. For example, the report that’s included in the Power BI Desktop file could have some visuals that you might want to share with everyone. Then, you create additional reports for each group of users and share them via dashboard sharing. This approach will work but if someone nukes the dataset, your reports go down with it. True, you can export a report connected to a dataset created in Power BI Desktop but who bothers to back up reports on a regular basis?
Then it dawned on me that you can connect Power BI Desktop live to a published dataset, just like you can connect to Analysis Services (recall that datasets published to Power BI Service are hosted in Tabular).
The major benefit of using Get Data->Power BI Service is that you can still back up the Power BI Desktop file and your reports with it.
Another benefit is that you can treat the published dataset as a “semantic layer” and let users create reports from it without importing data. For example, instead of asking users to call a stored procedure passing parameters and importing data, you can export all the required data and publish it to Power BI Service. Then, all users have to do is to connect to the dataset and start creating reports.