when to seriously consider message queues for backend services

Hey everyone, I've been thinking a lot about message queues lately, specifically for decoupling backend services. It seems like a pretty common approach, but I'm wondering when it actually makes sense to bring in Kafka, RabbitMQ, or something similar. When does it become more helpful than just, you know, adding more complicated stuff? Is it mostly for doing things in the background, managing sudden traffic jams, or is there another reason? What have you guys found are the downsides when you actually set these up? Really curious to hear what you all think!