I recall recently, from ESR's stuff hackers used to know article:
That property is still useful, and thus in 2017 the AT convention has survived in some interesting places. AT commands have been found to perform control functions on 3G and 4G cellular modems used in smartphones. On one widely deployed variety, "AT+QLINUXCMD=" is a prefix that passes commands to an instance of Linux running in firmware on the chip itself (separately from whatever OS might be running visibly on the phone).
As well as in TVs (e.g. my Bravia), synth workstations, etc. Once you take an interest in how stuff works, it is astonishing how ubiquitous Linux has become. Some point to the 'dont make money in those areas' arguments, but forget history and the consequences when cheap commodity and consumer goods become good enough in an area which was previously the preserve of high end equipment.