Teams: Can you do private chat only?

When I was young, I had MSN Instant Messenger. I used it a lot. Some of my friends at used AOL. Others used Yahoo and ICQ. Let's be honest - chat has always worked - and in many ways, we can be defined as the instant messaging generation as opposed to the email generation. There is a real beauty about an app that just focuses on chat - forget for a moment about all the bells and whistles. Remember back in time. Why did that chat apps work? Why does WhatsApp work? And Twitter? And Skype?