I think it's valuable to show how an "old, traditional"[1] system like postgres can actually be much more flexible and powerful even working in a fashionable environment.
If nothing else, it's a great exercise to make sure that postgres isn't missing out on a real, fundamental use case. Fashionable technologies don't always have something new to offer, but sometimes they help you see something from a new perspective.
[1] Postgres is very non-traditional in many respects, and I personally believe it's revolutionary; but many people perceive it as more traditional.
If nothing else, it's a great exercise to make sure that postgres isn't missing out on a real, fundamental use case. Fashionable technologies don't always have something new to offer, but sometimes they help you see something from a new perspective.
[1] Postgres is very non-traditional in many respects, and I personally believe it's revolutionary; but many people perceive it as more traditional.