Everything is a waste of time depending of the observer. For me Twitch is a waste of time. Watching TV shows like Jimmy Kimmel's is also a waste of time.
Sure, modern games have tended towards story, so watching Twitch/Let's plays is understandable for people who can't or don't want to spend money on them but have plenty of time to burn (I guess mostly kids/teens). Others just want to see some gameplay before deciding to spend their money. And there are some that like the commentary/reactions of the uploader. Even in Korea apparently watching streams of people eating is popular xD







