Do you think your phone should ring once? No, you want it to ring until someone answers the call. So, wouldn't you want a new chat notification to ring until someone answers the chat?
I get notifications from Teams, and my softphone, and emails, and many other programs. A single popup or "ding" is grossly insufficient to ensure new chat sessions are answered in a timely way. I can tell you that I have chat requests waiting for as much as an hour because nobody noticed the "ding" and the popup got lost in the many other notifications we get from other applications.
We need an option to enable "continuous ringing" that plays until someone responds to a live chat request, otherwise, the chat feature is a frustration to our customers rather than a useful tool.