It allows different teams to write in different languages, have different deployment cadences and different testing mechanisms.

The overhead of network calls and its attendant problems can be a worthwhile price to pay if you need to loosely couple your teams.

This is why my yardstick of "should it be a micro service?" is "could it work as an entirely separate business?"

I was a massive skeptic of micro services until I saw that it actually solved some people problems pretty well despite incurring a technical cost.

I'm pretty convinced it's an anti pattern in small startups though.

I believe network calls are a looser contract than function calls that would be checked at compile time, so it allows a softer decoupling between multiple teams. Compatibility or intermittent failures are handled with different strategies (rollout, rollback, deadletter queues) instead of impacting release cycles.