I assume they're there to write innocuous replies then occasionally shill for a product or push a political cause. Reddit is full of them.

YouTube's creator AI assistance leaking across universes? (If you haven't seen it, LGR did a video about the AI reply-to-comments stuff that YT is pushing - https://youtu.be/26QHXElgrl8)

I’ve never really been anxious about dead internet theory until watching this video. I guess I just never had knowing exposure to it. Surreal dystopia.