Peer reviews is largely done for free. In some cases, an author needs to commit to reviewing someone else's work for their work to be reviewed. However, this has led to an increase in LLM usage for review generation, even if conference/journal guidelines forbid it. I've seen nonsensical reviews from people who obviously haven't read the paper beyond an LLM-generated summary. Area chairs are supposed to catch this, but I imagine they're using LLMs too.