Well, some streamers still use this and some of their audiences are using it too, I just find this idea good because it helps you support your favorite content creator and at the same time getting some reward for it. Maybe if they used bitcoin as a reward, I think many will flock.
Depends, Bitcoin seems to encourage those that seek privacy to use it. Therefore, a platform awarding Bitcoin, might not be the best idea especially since this platform would have little reason, other than providing Bitcoin compared to the competitors. I do believe, users on the popular streaming sites allow you to accept donations via Bitcoin, so there's already a place that you could accept donations via that. I think I've seen streamers at least put it in their description if not within the stream itself.