TLS means Transport Layer Security, and people would do good to remember it was not invented to be used in the HTTPs browser webserver configuration exclusively. For that particular application though, it doesn't make sense to use a self-signed certificate as you can't control the client side and modern browsers will raise hell.

There are however many applications where a self-signed certificate (chain) is perfectly fine and even preferred. Think of mobile apps where you have control over how certificate validation is done on the client-side.