verizon is working on that: VoLTE
It's just to simplify their back end and will largely be transparent to users. It's kind of similar to how most long distance calls are converted to IP at some point as it's much easier to manage, but that largely hasn't stopped long distance companies from charging by the minute.
Verizon and AT&T has largely done what you both want. They don't count minutes and text, but they now meter data. The fact that it will eventually all be data in the back end is irrelevant. If you think that either one will ever go completely flat rate for all three, or think they will officially call it all data to their customersI have a bridge to sell ya.