One could argue that the whole point of traditions like Christmas is to have comforting, repeated experiences like listening to the same music each year, something to ground your mortality in timeless rituals that started before you were born and (you hope) will continue after you die.

That said, there is lots of Christmas pop that doesn't make it into the canon. I have no recollection at all of the first song on the Christmas tape, and i was around then (and going to K-Mart with my mom).

I think it's a combination of copyright and licensing.

The pop music they use on these tapes are cheap to license --- they weren't even popular when they were contemporary. They were just generic cheap music.

For Christmas, there is a set of Christmas music that just gets played every year and is licensed in blocks that are fairly cheap. That's why you hear a lot of "traditional standards" and not much else.