API Gateway versus making direct calls to services. When should you pick one over the other?

Hey everyone, I've been thinking a lot about how we structure our service-to-service communication. Sometimes it feels like an API Gateway adds unnecessary complexity, especially for simpler setups. But then again, for more complex scenarios with many services, it seems invaluable for auth, rate limiting, and routing. What are your go-to strategies? Do you usually put an API Gateway in front of everything, or do you prefer direct calls for internal services and only use a gateway for external-facing APIs? I'm really curious to hear your experiences and why you choose your approach.