When should you start using message queues?

hey all, been thinking a lot about decoupling services lately. we've got a few synchronous calls that are starting to bottleneck, and im considering adding message queues to handle things asynchronously. but it feels like a big architectural change. when have you all found it makes sense to introduce message queues? is it purely for performance, or are there other use cases like buffering or guaranteed delivery that tipped the scales for you