What do you mean by "arbitrary stream of text"? I fail to understand, to be honest. A text always need to be parsed, even a simple number, but the point is to deal with characters instead of raw binary data.
>What do you mean by "arbitrary stream of text"? I fail to understand, to be honest
That it's structured and specific.
UNIX pipes, for example, can deal with any kind of text -- it's up to the user to ensure that the commands (e.g. "cut -d," etc) work ok with them, whereas the JSON RPC communications of the language server are not only in a specific syntax (JSON), but they also have predetermined content schema.