Much as most everything is still a "serial port" long after actual RS232 connectors went out of style the simplest level most radio hardware offers to interface at is - you guessed it - some variation of AT commands over a serial connection. Even the recent ESP8266 all-in-one WiFi module does the same. That is not to say many of these modules don't offer more complex ways to interface, but the AT commands are always the first level offered. I guess it's not a praise for the makers of the drone that they stayed at that level, but hey - the simplest thing that works tends to win, isn't it...
