I still like POTS
I sometimes still think about getting a POTS line installed at home, and wish I had it at the office as well. I just don't enjoy talking on the phone any more as the service is typically delivered today, via VoIP or whatever other protocols might be in use.
There's that little bit of lag, always. There's that "CATNAP" sound quality (a mobile-home industry term: cheapest available technology, narrowly avoiding prosecution). To a hearing-compromised person (as more and more of us will be over the coming years), that's the worst part of it. And there's the dropouts, slapback echo and entirely dropped calls. And finally (off the top of my head) there's the security/confidentiality considerations (i.e. there is none).
So while you can do telephony without the phone, it's just not what it could be. Compare a typical Skype PC-to-PC connection, where at least the sound quality sounds like you're sitting in the same room with the person (although there are still the lag and other problems), for the high bar of what can be achieved, and the typical cell phone to cell phone connection where every call is a series of "can you hear me now," or "excuse me," or "can you repeat that please?" for the low bar. It's a huge gap.
The whole calling experience becomes counterproductive, frustrating, and just makes people sad instead of happy. Other than that, it's great.