Actually I think it's quite common, it applies to any site not busy enough to justify a dedicated server. By the long tail principle that will be the majority of sites on the internet.
Oh, I should be clear, I'm specifically talking about sites sharing a certificate. I know a lot of sites use shared hosting, but it's awkward to get a certificate for a pile of unconnected sites. Most of them will either not support HTTPS or require paying a couple dollars for an IP. (Or, these days, try to rely on SNI.)
