The historical origin that I learned for UNIX was that it was created mostly out of frustration with Multics, and that its original "primary" use was running one of Ken Thompson's video games[1]. It was originally written for a PDP-7, which was already obsolete at the time and probably wasn't a target for telecommunications software.
It was only much later (and after significant arm twisting for more computing resources) that AT&T took UNIX seriously. Even then, the first marketed versions of UNIX were oriented towards programmers and technical editors, not telecommunication[2].
[1]: https://www.bell-labs.com/usr/dmr/www/hist.pdf
[2]: https://en.wikipedia.org/wiki/PWB/UNIX