Presumably one reason to use this is latency: materialize is built on differential and timely dataflow, some innovative frameworks (by Frank McSherry, who was at Microsoft Silicon Valley Research back in the day and is elsewhere on this HN discussion) that are intended to reduce the amount of computation in certain kinds of calculations. Materialized views are particularly ripe for those advances.

It's also written in rust instead of Java, so there's no JVM RAM penalty or GC to contend with.