[ahoka]

Most applications read JSONs from networks, where you have a stream. Buffering and fiddling with the whole request in memory increases latency by a lot, even if your JSON is smallish.

[Rapzid]

Most(most) JSON payloads are probably much smaller than many buffer sizes so just end up all in memory anyway.

[mgaunard]

On a carefully built WebSocket server you would ensure your WebSocket messages all fit within a single MTU.