It seems like a notion that started in the early internet and just refuses to die.
Everything on the internet is minified and compressed at this point, so the entire idea of "human readability" left the station years ago. Yet I'll still see a primary complaint against the likes of http2+ being "it's a binary format! On NO!".
JSON seems like a similar relic. We use it not because it's fast, but because we like the idea that it's easy to decode (Even if in practice that almost never happens).