I use Kafka because it has almost infinite scaleability in terms of processing events (could be scaled to process hundreds of thousands of events), great monitoring (all sorts of metrics are exposed via JMX).
Downsides of using Kafka are: - you have to deal with Zookeeper - you have to implement advanced routing yourself (compared to RabbitMQ it has no advanced routing)
Kafka was only introduced to our platform in August 2018 as a means to manage our data pipeline and to replace other messaging systems used to decouple various components in our system. Kafka provides the scale and storage we need to manage data for however many devices we might service. Additionally, Kafka has helped us lay the framework for improved and highly detailed statistics gathering and analysis.