While true, it's still a text and usually http/tcp based format; data -> json representation -> compression? -> http -> tcp -> decompression -> parsing -> data. Translating to / from a text just feels inefficient.

With projects I work on it's over websockets, js/ts has builtin support, easy to log, debug, extend/work with etc.

Binary protocols have exactly same steps.

Redis is also using text based protocol and people don't seem to be bothered too much about it.