With digital encoding, you have a defined bandwidth you have to care about (the audible range of frequencies), which puts a limit on how often you need to represent the state of the wave.

Also, digital transmission does fancy things with phase, amplitude, and frequency combined to represent multiple bits at once.

> less efficient

In what sense?

> because because transforming sound waves to electro magnetic waves was more straight forward

This sounds like you might mean power efficiency. I don't know if that is true or not.

But in this case they are talking bandwidth efficiency.