For me, I think it's that I consume text much faster than e.g. video or someone talking, and it doesn't distract me.

I just want to be left alone when I want to focus and learn things. I love using ChatGPT to explore a subject now, though, because it's pure text and I am driving it, so I can totally see people who are more visual and social learners want something similar "packaged up" in an avatar.