It was to do with the subscribers and cost of fiber-optic. Now we have air travel and the world is a smaller place. It is easy to get international phone calls. Thank goodness.
The history and development of this, is only as old as me. So we are still developing the technology to local applications when the cost is ok. Have a read of how we can talk to our mahals so far away.
The first transatlantic telephone cable to use optical fiber was TAT-8, based on Desurvire optimized laser amplification technology. It went into operation in 1988.
Read more about it if you are interested
Source- Wikipedia- History of Fiber Optics
