If I remember correctly, it was the same in Mexico and Scandinavia and some other countries. While there are ways to disable the subtitles through unofficial means, I doubt that they still work.

It is quite possible that this is due to licensing issues. This link here https://mrgnome.wordpress.com/2013/11/02/no-option-to-turn-o... might or might not help you, given its age.

In some sense it is still better than Amazon Prime in Germany with only German audio being available when I was using it last.

Do you know whether the same thing happens with Netflix original content as well?