Adding support for closed captions via WBTVD.com or the WBD Screeners app is a feature we are actively working on.
We hope to implement closed captions on any newly published asset on a go-forward basis and retroactively bring legacy content into the fold. With over 80,000+ assets this could take a while! You'll notice captioning is more prevalent on the latest content while our legacy content may not yet have captions available.
If there is a business need for closed captions on a title, please reach out to our team with more information and we can help advise.