Cannot Extract Subtitles from .VOB files

[ToiletDuck]

Never encountered txt,srt.. based subs... in any form, size or scent in my huge dvd/bd library ..

Like I wrote, cc (EIA-608) subtitles are not so common on DVDs

Big studios often do not add CC user data subtitles since it is an extra, not mandatory step.
You can read the standard if you don't believe me. If you want to better understand DVD related stuff without reading the standard, 'DVD Demystified' (<- the book) is a good read.

Cu Selur

I wouldn't be surprised if that does exist on some dvd sources..
And like you wrote, it has been done in rare cases... 

Hence and again , hard to imagine to find a example in one's collection..  It's not that i NOT believe you