First of all, I confess, I have never actually used a chat room! Although I spend a lot of time in on-line forums like this one. So what I write here is from an understanding of what a chat room must be like -- not from any actual experience. These are the issues I would have with it:
1. Time zone differences. Some of us are in wildly different time zones. If my bed-time conflicts with chat-time, bed-time wins. Work-time wins too, unless you have a very understanding boss.
2. Archive and search abilities missing? Would we even want to archive most of the chat?
3. How do we red-flag a minor? Do we even know who they are?
4. I like to consider what I write, pay attention to speeling and gramma and make sure I am as clear as I can be. Don't think I will be able to do that with chat.
5. I like the time slippage of a forum like this one. Any member can come in any time of the day, post something and others can read it whenever they like, at any time of their day -- or week.
But having said all that, I would be happy to give the chat-room a try. I think a major stumbling block will be setting a time that suits most potential participants.