so, when do you actually need to ditch simple API calls for a message queue

hey folks, ive been thinking about our service-to-service communication. right now, most things are synchronous api calls. it works fine for simple request/response patterns. but im starting to see cases where a service might take a while to respond, or we want to decouple producers from consumers more explicitly. when did you all make the jump to using something like RabbitMQ or Kafka? what were the tipping points? curious to hear your experiences