At 13:30, he starts talking about HTTP between services, and some of the issues with it. He specifically calls out the JSON, because it does not have types, it can be a big mess at scale.
At 16:03 he finishes talking about that by saying that if you own both sides of the interaction, just treat it as a function call, don't treat it as the server being, basically, a web browser.
At 23 "We just have HTTP and JSON. That's how our services interact. Even though we have hundreds of services for this TODO app. It's dumb and it's inefficient. You can read it on the wire. ... you can totally understand what's happening on the services if you can see them. ... It was more important to me that the system was easy to understand than efficient.
Doesn't give a super-strong reason for using it, but talks about using Rabbit like we do in Hub here: blog-post-microservice-communication-with-queues