Occupational classification is a matter governed by national statistical bodies in different countries and is the subject of international agreements. Getting anything changed can be a long and hard struggle, as various different bodies need to agree.
The STC has made some progress in the United States on the question of professional recognition for technical writers. After several years of negotiation with the Bureau of Labor Statistics, STC has persuaded them to accept that what technical writers do is different from what other kinds of writers may do. According to a recent press release, the next edition of the Occupational Outlook and Handbook will include a separate report on technical writers.
This is good news, as it sets a precedent that may eventually be followed by the UK's occupational classification scheme, which still lists technical writers alongside "artists".