Here's a fun graph for you: number of christmas albums released per year since 1940. Starts off fairly low, then, starting in the early nineties, the numbers begin to skyrocket, peaking at 70(!!) in 2008, with the numbers declining heavily since then. I wonder what's up with that? I mean, Mariah Carey didn't help, but she alone can't be responsible for that peak a decade and a half later, can she? The world may never know...
I guess part of it is that no one really cared. If you look at the most popular holiday songs, the newest song is Mariah Carey in 1994 (and a recording of some older songs from 1995). Despite the dozens upon dozens of Christmas albums produced over the 2000s, none have managed to really worm their way into the popular conscience. So, if no one's gonna care, why bother? But, that's just one possibility.
Anyways, this has been incredibly lazy, completely pointless data analysis with Aura.