The questions only concerns the following languages:
English, Dutch, French, German,
Italian, Japanese, Korean, Portuguese, Russian, Spanish
After reading YouTube's official documentation, it would appear that all videos have automatically generated subtitles. However, for example this video doesn't have captions of any kind.
Review, edit, or unpublish automatic captions
If automatic captions are available, they'll automatically be
published on the video. Automatic captions may not be ready at the
time that you upload a video. Processing time depends on the
complexity of the video's audio.
Best Answer
You sort of answered your own question. IF YouTube can generate captions for a video, you'll see them. If they can't, there won't be any automatic captions. Also, if the channel owner doesn't want automatic captions on the video, they can remove them from view.