Most European films from 1973 are still under copyright. The rights to 14 und unter may be held by a defunct studio, a private estate, or a forgotten distributor. When a film has no clear rights holder, streaming services avoid it, and legitimate download stores (Amazon, iTunes, Google Play) cannot list it.
The film was part of a wave of European "enlightenment films" from the late 1960s and early 1970s—movies intended for adult education about teenage development. However, due to its subject matter and the ages of its actors, the film has been historically controversial. It never received a wide release in English-speaking countries, and it has never been officially released on DVD or Blu-ray in Region 1 (North America). 14 and under 1973 movie download work
For those looking for a legitimate way to watch or download the movie: 14 and Under (1973) - Full cast & crew - IMDb Most European films from 1973 are still under copyright