Because transactional workloads (many small reads and writes that require consistency) look different from analytical workloads (giant reads with a small number

Because transactional workloads (many small reads and writes that require consistency) look different from analytical workloads (giant reads with a small number of columns with looser consistency guarantees). OLAP databases typically use a column store which is amazing for reading a subset of columns because of much better compression and use of vectorized execution as opposed to Postgres’ tuple-at-a-time execution. The tradeoff is it’s expensive to update a column store since you have to rewrite a chunk of the column at least. Postgres is moving towards better OLAP. AlloyDB is a recent commercial DB that swaps out the Postgres storage engine to better support OLAP. That said, you can coerce Postgres into doing a reasonable job at OLAP for a surprising amount of data.