You know, because the M-rated Resident Evil: Revelations Collection featured on the store's landing page is appropriate for everyone. Especially compared to utterly gruesome fare like party game Animal Rivals and the "relaxing puzzle game" ERMO.
Much like the program's predecessor on Xbox 360, this wall, as minor as it might seem, cordons off the high-profile indies Microsoft has a vested interest in pushing -- and limits potential income for developers -- from the ones anyone can publish on the system. I digress. The offerings has grown since the Creators games were available in limited fashion, and a vast majority of them are free. The most expensive title is Derelict Fleet from developer Bionic Pony priced at $9.99. For more info, check out Xbox Wire and the video below.