IRC has major issues, actually - notably, it's very tricky to parse correctly (and very easy to think you're parsing it correctly when you aren't), and doesn't support more than one space-containing value per 'line'. It's also implemented differently by every single server.

You will need some kind of serialization format for a reliable message protocol. JSON is just the simplest possible format that can reasonably represent common data, and works in 95% of the usecases.