WebSocket is more well known than SSE, and it's also what Socket.io uses, so I think this isn't always a conscious choice. Developers are still discovering that

WebSocket is more well known than SSE, and it's also what Socket.io uses, so I think this isn't always a conscious choice. Developers are still discovering that SSE is a thing. Another factor is that most apps using a socket-ish connection tend to run almost all traffic over the socket as opposed to just "push" traffic. This can make sense if the exchanges aren't very resource-oriented compared to a REST API.