So maybe I'm missing the point of the
SLU group. I thought it was a social group and a way to keep up with events put on by regular posters here. A good way to do that is notices.
If I log on after the event has started, and the only notification was via chat, I will not know about the event. So chat is only good for those users logged on at that time. The person in charge of the event is left with either no means of notification to those who aren't lucky enough to be on at the time of group chat notification or s/he must spam the group chat repeatedly to get late-comers.
Add to this problem that anyone who dislikes notices can easily opt out of getting notices and this seems like a suboptimal solution.