Businesses are 24/7. This includes everything from the website, back office, supply chain, and beyond. At another time, everything ran in batches. Even a few years ago, operational systems would be paused so that data could be loaded into a data warehouse and reports would be run. Now reports are about where things are right now. There is no time for ETL.
Much of IT architecture is still based on a hub-and-spoke system. Operational systems feed a data warehouse, which then feeds other systems. Specialized visualization software creates reports and dashboards based on “the warehouse.” However, this is changing, and these changes in business require both databases and system architecture to adapt.