I personally don't think an official telegram group is necessary - but for some small group of people can create their own for one reason or another. Bitcointalk is more than enough for me if the purpose is to have discussions - but of course not all of us can be active all the time in front of the monitor to respond to everything. Social media like Telegram is certainly good for quick response from users - but I think it can easily turn into a haven for scammers.