I'm not going to add it.The adult content is reachable through the web browser so It shouldnt be a problem to make it work in the plugin...
1) I don't want to add it
2) There's going to be a lot of extra work to do it, extra api calls, extra web browser automation
3) I have to mark the site as "Adult", then the users needs to enter pin to be able to use the site (or disable adult or pin). Hence low usability and annoyance.
But you or anyone else that are interested could do it, the site is open source, and publish as a new site.
And, there are plenty of adult already in OnlineVideos