Note that many streamers do not use a webcam, or don't show their faces on camera. Some do use a camera but still conceal their basic personal information.
There are benefits to streaming. It somehow makes you productive, because you don't want to look bad in front of your audience.
Plus, there are smart people on Twitch. A lot of lurkers that do not stream have an impressive amount of knowledge.
Money-wise, it's not worth it. The category that has the most programmers, "Science & Technology", has only 2,000 viewers at a time on a good day. That is very little compared to other categories. If you want to make money, publishing YouTube videos may be way more profitable than Twitch.
