>>107626648Because if you think long and hard about what to type in chat you might realize the first thing that came to your mind would be inappropriate or pointless, and you end up not saying much all that often. Conversely, if you type and hit send before you think, you end up chatting a lot.
Because of that, any given chatter might fall into either of these groups depending on the day, but chat as a collective entity seen through the eyes of the streamer is always going to come off as immature. Or so I'm guessing.