It's simple. First we got the landline telephone. Then we got mobile phones. Then we got Internet-connected PCs. Then Internet connectivity was added to mobile phones. Then we got applications and apps that let us make calls over our Internet connections.
Now we don't need phone service anymore.
I know that Internet-based, or voice-over-IP (VoIP), service has a longer voice delay and is in that way worse than your typical mobile phone call. And, for that matter, landline phone service offers higher quality than a mobile call. (And records are higher quality than MP3s. And letters are higher quality than email. Yet we routinely choose lower quality in some respects in order to have more features and lower cost.)
The truth is that Internet-based phone calls are good enough. There's a delay, but the sound quality can be superior. More to the point, voice communication itself has been sidelined for most communication. Young people are gravitating to IM or social network messaging. Business people and others are embracing video conversations. All kinds of apps are providing innovative voice communications that aren't phone calls, exactly.
These "intercom," "push-to-talk" or "walkie-talkie" apps are cheap or free, and so common as to be a banality.
For phone conversations, we can use Google Voice, Google Talk, FaceTime, Skype or any number of similar VoIP apps.
My preference by far is Google Voice. It lets me set up custom voice-mail greetings for specific people or groups of people. It sends my voicemail and text conversations to my email inbox. It lies to telemarketers for me, faking a "this number is no longer in service" recording. It enables me to do both calls and SMS text-messaging via a browser on my laptop, if I want. It's secure because I use Google's two-step authentication.
Google Voice is not a pure VoIP service. It jumps in and out of the normal phone system for various purposes, which makes the service slightly more feature rich. But a great Internet-calling service does not need a phone system, just the Internet.
Google Voice has a long list of features that I've wanted from my mobile carrier, AT&T, for years, but they've never delivered. AT&T has been too busy throttling my data usage and trying to keep me from using alternatives to its exploitive SMS service.
The difference between AT&T and Google highlights exactly the problem with the old model for phone calls and the new one.
Why I want Google to provide phone service