Ok, but what if you want to transmit two streams? You'd get something like Interlaced-newline-delimited-JSON. And so the list of required file formats knows no end.

The only reason people care about newlines for a stream is because they've arbitrarily chosen to fetch bytes from the stream until the next newline sequence (readline instead of read). But you could just as easily look for a different sequence, like the ASCII record separator character which was invented exactly for this task, and then you wouldn't have to destructively strip newlines from your input.