Disney alway felt there were somehow above other studio when it came to videos and now DVD. They only limitely release something then not release it again for year.
Porno? I dunno. I guess they want you be able to see as many sceen shots as possible because what you see on the back on the box is what's usually gonna make you rent or buy a porno. The back of a regular move video's tape box isn't what's get gonna you to rent/buy it for the most part.
Those are just my theories.