closed captions

I am wondering why PBS shows that already have closed captions on the web do not show captions when you look at it thru a Plex app.
Seems the apps should/could pull the captions straight thru so that we can see them? Then if we are a pass member, record what we want to with captions. My on TV media that was saved with cc works fine when I via through Plex on pc or other device.
Without the captions, many people who need captions will need to seek another program so we can have access to captioning (when the programs are already captioned).