[tomnipotent]

C-store's 1) improve aggregation performance since values are continuous on disk/memory for the same column and 2) benefit from bitmap indices when not doing range queries. Why do you think c-stores make a difference for the T stage? Because the performance overhead makes views viable?

[thingsilearned]

Yes, and also the whole process is much simpler to pull the T out. The reason T had to be done at the same time as E&L was because of those storage and performance costs. Now you don't have to - and it separates the stages and simplifies.

The T being after the L means you can do that stage more simply in just SQL (with views or materialized views - possibly with the help of DBT), as opposed to some vendor interface, or python/R/etc script.

It also means that rebuilding your warehouse is much less significant of an ordeal. When the structure of source data changes or if you want to make some migration of the schemas of the warehouse you don't need to also re-run your ETL jobs and start over from scratch.