Indeed, internal communication is often treated differently. Even at my company we primarily use ZeroMQ between microservices, because it's fast and our (small) team understands it.

The movement behind the HTTP ecosystem is undeniable though, and the common practices for public APIs are moving internally. You might check out an API conference or meetup sometime to see what I mean (not that any of us are obligated to follow this trend; I'm just bringing it to light).