True, but why? I believe you, but I'm not sure why? It's not because of inferior quality (since it's technically a mainline game), is it because it was marketted differently as Rol said? Is it because it's on a portable with antequated graphics as compared to what the mainline series is used to? Is it because people just don't buy non-mainline entries? So I believe you, I just can't wrap my mind around it .
The Resident Evil fanbase is another example of "hardcore" gamers. They want best possible experience, high quality graphics, lots of blood and gore, a competent online system, and a home console that's not labeled as a child's toy. It's why PS3 or 360 are the preferred platforms for games like Resident Evil or Call of Duty. As you already know, 3DS just isn't a platform that appeals to this type of audience. You could say that Monster Hunter sounds like game that fits this criteria, but local play is integral to fully enjoying Monster Hunter, and it appeals to a much wider audience. And Revelations not having a number in the title just makes it seen as another spin-off and lowers it significance even further. Besides, the series was born on PlayStation consoles, and has always been the go-to brand for RE. This is the first true survival horror RE in years, but on a handheld. A Nintendo handheld. There's just no market for it on the 3DS, though I'm slightly surprised Revelations and Mercs. 3D sold as well as they did.