Ideally? Automatically answering support questions in open source discord channels, automatically taking minutes in business slack conversations.
Cynically? Your group chat is hosted by a tech company. That tech company wants to tell investors they've got an LLM, and show user counts going up. And the fastest way to boost user counts on a failing product is to make it an always-on feature of a successful product.
Is that the only thing you talk to your friends about?
I mean yeah literally you could talk about your plans [i.e. by yourself or with the other real people] or what's going on in your life and have the bot chime in with thoughts too. You could talk about food, philosophy, politics, travel, complain about stuff, get advice for relationships or work, gossip. All in a group chat setting.
It's not hard to imagine a bot that's able to contribute here and there in a meaningful way in any of these subjects, and other unlimited subjects. But perhaps you weren't open to it in the first place so I'm not going to try to convince you further if you don't buy it; If you don't want to really give it consideration then nobody is going to convince you otherwise.