I don't usually speak a lot unless I'm having conversation, or at least starter for it.
It's certainly not a requirement, it's your stream, do what you want with it, but I do think it's a "best practice" for streaming and getting followers and more viewers. Keep in mind people can find other streamers to see the game you're playing but they can only go to you to see YOUR commentary of the game. If it helps you, keep in mind that people can watch the stream as a VOD after the stream is over. I have a friend who watches my VOD from the previous night while he's at work during the day. Even if nobody is chatting I try to keep the commentary flowing.