Old people, man. And the people who take care of old people. I know it's not typically HN target demographic, but old people need improvements in their lives, too.
I thought BCC was aimed at teachers? Various implementations of bingo are commonly used as teaching aids, test review games, etc.
Though I agree I'm amazed at its success. It's one of those ideas I'd have dismissed as "you could never make money doing that."
Not old people. Teachers. The distinction is vitally important. BCC solves a professional problem that teachers will pay money for. It's not about entertainment.