I don't expect the host to drop everything to respond to messages but it would be nice if every few minutes or 5 or 10 minutes they responded. It's understandable that they're busy drawing and won't make much progress if all they do is talk.
I definitely find it more enjoyable, but not necessary. They are trying to get things done, after all. Most of the time I'm just awkward and don't really know how to start a conversation/keep a conversation going, or I'm doing other things besides watching the stream, so I don't chat much myself.