I really like this example. A lot of databases have very good module separation internally. However, you don't often see people splitting out query planning, storage, caching, and etc into separately hosted services forced to communicate over the network; even in modern distributed databases.

Meanwhile, you also don’t see a lot of people claiming you should have one single repository that stores the source code, configs, CI tooling, deployment tooling, etc., for Postgres and Mathematica and the Linux kernel and the Unity engine, or that operating any one of these kinds of systems should have anything to do with running any other system apart from declared interfaces through which they might choose to optionally communicate or rely on each other as black box resources.