I'm not very familiar with Twitch, but isn't the community interaction (text/voice chat?) a large component of it? I'd imagine these streamers would be very interested in chatting with the 1 or 2 people who stopped by their stream.
If the bots can't respond they'd be found on pretty quick, and making bots who can pass some sort of "video game specific Turing test" is a major endeavor. Only getting instantly recognizable fake viewers would as demoralizing as no viewers.
Yes and no. The thing is, the majority of the viewers usually doesn't write to the streamer. They simply watch the stream, nothing more. So having five real viewers but no one is writing anything (or answering) is definitely possible. Still, interacting with viewers is where it gets interesting and it is live-streaming after all, so that's actually the point (otherwise you could just create a video and upload it somewhere).
I would think that the ratio of "interactive" viewers is higher for streams with less viewers (because of the different atmosphere, non-professional streamers being able to interact more personally with the audience...).
If the bots can't respond they'd be found on pretty quick, and making bots who can pass some sort of "video game specific Turing test" is a major endeavor. Only getting instantly recognizable fake viewers would as demoralizing as no viewers.