Electronically, a digital signal requires that we convert our analog signal to a digital one in an audio-to-digital converter (AtoD). And we have to convert it back at the other end. We can do all this, but it takes extra stages and effort to make it happen. Certainly it's the only way we can move all the signals we need to move, like with cell phone traffic. Without digital techniques, we'd be dead in the water trying to serve all the cellular customers we serve, but voice traffic starts and ends as analog signals 'cause we human critters can relate to them better.