Pure old copper-line phones did not need a working power outlet in your home - electricity was introduced to the system at facilities of the phone company (often miles away), and often used a dedicated electric grid.

With VoIP, you tend to have your own, plugged-in wall box. Which becomes useless the moment your electricity stops, e.g. in case of natural disasters.

Also, analog telephony just sounds better than digital one. No downsampling happening.