Over 2G and 3G, voice calls are circuit switched. VoLTE and VoNR are packet switched, over IP, VoIP. Totally different. VoLTE is not as standardised as it may seem from the outside whereas 2G and 3G voice calls were.
Internet access is not regulated as an emergency service.
It’s easy to forget that our pocket computers are also telephones, and thus emergency calling devices. These are regulated with good reason. The operator/their partners have to test the device on their network to ensure it is compliant and emergency calls can be made as expected; they also need to build the VoLTE/VoWiFi/IMS settings for that specific network into the handset’s software before it will work - VoLTE has many complications, it is not one size fits all. Accordingly, some operators allow BYOD, while others will only whitelist the specific hardware and software combination they have tested and signed off on.
The US market has three big gatekeepers named Verizon, AT&T and T-Mobile. They charge huge money to certify devices to work on their networks. No certification and phones won’t work properly for mission-critical stuff like VoLTE, VoWiFi, and in some cases 5G. Without these features, no-one will buy the phones.
You also need to be selling a big number of those phones to eat the cost of all that certification. And what do you know, the telcos operate the stores that sell the lion’s share of phones in the US market.
All that adds up to niche handsets only working on 1 or 2 of the telcos, or only partially, and only selling direct to consumer or on Amazon or Best Buy or wherever in negligible numbers.
And that’s why you can’t buy a Fairphone at retail in the US.
The smell of fresh bread is like a hug for your nose.
A breadmaker which also makes jam.
That is not the slobster I was expecting.
5G NSA does have the same problems since it’s 4G with a 5G hat on, although the handset-side software stacks for IMS settings are slowly improving. 5G SA is still too new really.
5G theoretically replaces 2G for low-power machine-to-machine operations like connected power metres, which is the main reason 2G still exists, but of course requires new hardware.
The many joys and customer issues that happen when an older network tech is retired and the spectrum refarmed to the new standard (e.g. shutting down 2G/3G and using the bandwidth for 4G/5G) are well-documented and a smart operator can do it with comparatively minimal friction, it just takes a long time to do it right.