Netflix doesn’t make all subtitles available in all locations. I am not sure if there are contractual georestrictions on subtitles. I expect the answer to be that it depends on the show.
I think when there are no georestrictions they limit the number of available subtitles out of convenience. This way you don’t get a long list of available subtitles to choose from.
This causes a problem though. In Germany they don’t show Arabic subtitles. The closest they could get to a minority is Turkish and Russian. In Japanese anime it is worse, they only show Germany subtitles. Not even English.
I really hope someone at Netflix fixes this.