Following the release of Quentin Tarantino and Robert Rodriguez's Grindhouse, there was a resurgence of Grindhouse/Drive-In/Exploitation films on home video. It appeared at the time to be a quick cash-in on Grindhouse's (mild) success in the theater. DVD video companies started releasing a slew of 70s/80s smut movies, often as double-features. I got hooked on BCI's "Welcome to the Grindhouse" series of DVDs. My absolute favorite is Malibu High/Trip with the Teacher, with The Beach Girls/Coach at a close second.
Their releases often had themes such as "black magic" or "school's in session" for the two films on the disc. They quickly discontinued this series, but replaced it with the extremely similar "Exploitation Cinema" double-feature DVDs.
Then came another similar DVD series called "Roger Corman Cult Classics." These are all either single, double or triple-features.
The website Mr. Skin has even gotten in on the action.
So basically this has resulted in a lot of really obscure exploitation films being released on DVD for the first time and being celebrated in an unabashed presentation.