These days, unless you're on 2G or 3G (if they're even still available in your country), mobile phones will often use AMR-WB or EVS when calling over IMS (i.e. VoIP over LTE or 5G), which are both wideband and considerably better than G.711 (and probably even G.722; while they have lower bitrates, they're also considerably more modern).

The problem is that when calling across networks, the connection might still go over a legacy circuit-switched exchange, and that compresses everything down to narrowband again.

I hope that whoever regulates the PSTN in the US will force a switch to all-IP interconnects at some point, since now we get the worst of both worlds (often somewhat lower reliability due to badly managed VoIP services, combined with potato quality because of a legacy interconnect somewhere between VoIP networks).

All IP could also provide much more efficient routing: Right now, as I understand it, if you're calling somebody with a 212 area code and both you and the callee are physically in San Francisco, your connection might still be routed through some circuit-switched exchange in Manhattan, which isn't great for latency or high availability.