AT commands are still in use inside your smartphone. On an iPhone, when the main CPU wants communicate with the baseband chip to make a call or send SMS or whatever, it literally sends AT commands.

In fact, one of the earliest iPhone jailbreak exploits relied on a vulnerability in the AT command interpreter inside the baseband.

Commands that have to prefixed with AT are still in use. Most of the actual commands after the "AT" part are not recognizable to someone who knows dial-up modems; they have nothing to do with the Hayes set other than the AT prefix/misfeature.

Yeah, that's what always confused me about it when I worked on GSM phones back in the mid-2000s - if you're going to overload an old protocol so heavily, it's time for a new one.

Probably nostalgia! That would be good enough for me.

At commands are used for many nonmodem things too.. Bluetooth adapters, zigbee adapters, HC12 transceiver, other various proprietary devices tied to a UART in addition to LTE, GSM/GPRS (I guess technically some of those are modems but they’re pretty far removed from the original design)

Absolutely! While it's not my preferred method of control, you can send AT commands encapsulated in SMS to update/troubleshoot BGAN terminals.

Iridium modems use it too!

Its embedded into GSM modules; Phones need it to do anything, to check firmware versions, to send and retreive SMS messages, to make calls etc. I used it to control the 3G dongle I had (basically, a GSM module in a stick). Most times the device will act as a serial device.

Also used in the esp8266 when it's configured in wifi-serial mode.