This is why sometimes you end up with BOTH a traditional ETL data warehouse, for common, structured reporting and analytics and also an unstructured data lake(s

This is why sometimes you end up with BOTH a traditional ETL data warehouse, for common, structured reporting and analytics and also an unstructured data lake(s) that pull raw data in from many sources to allow for ad-hoc exploration. But like others have said here, eventually you might find a novel pattern or something worth tracking on a regular, go-forward basis, and will want it to built into the data warehouse, for all of the various benefits a data warehouse provides for everything else it does so well.