For the same reason that they also include symbols for many obsolete (dead) languages and writing systems, as well as (per a comment above) a character used by

For the same reason that they also include symbols for many obsolete (dead) languages and writing systems, as well as (per a comment above) a character used by the 1959 IBM 1401 computer (https://github.com/shirriff/groupmark https://github.com/shirriff/groupmark). The need to be able to discuss a certain technology in writing does not disappear just because it is out of general use.