One practical reason we chose Nats over Kafka was that Nats doesn't need zookeeper for HA.

Nats doesn't provide message durability too, luckily it's not required for 95% of our use cases. Also, having NATS already implemented it's a natural move to use NATS Streaming for durability rather than introducing a completely new technology to your stack.

Less pieces - fewer chances something breaks.

NATS by itself is designed to be more of an always-on style queuing system (the term they use is "dial tone") but doesn't handle node failures by itself. If you're looking for a Kafka-flavored NATS, there's a new release I saw recently called LiftBridge that adds some durability to the NATS protocol.