It's there because of anti-discrimination laws. Job titles and occupations in German always have a gender associated with them (it's just the way the language is), but companies aren't allowed to discriminate. So it's shorter and easier to put (m/f) at the end rather than having to always list both gender forms of job titles every time the job title comes up.

English still has some of those gender forms for older professions. For example, there's waiter/waitress so instead of always writing "waiter/waitress" they just write "waiter" and then put (m/f) at the end to indicate that they will hire either gender.