Since Power Apps offers a wide range of connectors and puts all the data gathered from the data sources into tables, it would be awesome if you could exchange one data source for another and the app you created still works as expected.
Use Case Example:
An App is created with the primary data source being a SharePoint list. Now the company wants to move all the data to an Azure SQL Database. The tables would be the same, so the only thing which needed to change would be where the data is gathered, all the queries on the data could remain untouched. Currently in Power Apps (as far as I know, please correct me if I am wrong) you would have to delete the old data source, add the new one and basically rebuild all the parts which interacted with the data source.