Getting released on OCR is serious business, whereas someone might get 10 or so views on bandcamp, it'll get maybe tens of thousands, on OCR
Edit: I mean certainly if someone wants to make an album they would and should, but to make a large production for next to no audience makes it less worthwhile... to make something great for thousands of video game music listeners is the ideal scenario don't you think? Maybe someday OCR will have some kind of OCRS-0000 for solo albums.