I agree. And I love to tell this story. Excuse me while I bore you....
I had NEVER heard of this 1947 movie when I was a teenager in the '80s, and that's something since my parents managed to make me amenable to old things like movies on TV or music they played. But my parents knew it and IIRC early in the VCR craze rented it and said we should watch it, it is good and sweet. So I did and I liked it.
Then within the year, my social-studies teacher actually played this very movie in class, ostensibly because he could tie in the "savings&loan crisis" with the building & loan in the movie! LOL Anyway I was rather astonished, because again, this was a RARE movie.
But then, the floodgates broke. By the late '80s "IAWL" was suddenly the greatest Christmas movie ever, and as you wrote, now it seems about the only Xmas movie ever, along with "Xmas Story" (also 24 hrs straight at Xmas).
Before the late '80s, noone KNEW "IAWL". Back then, the end-all be-all Xmas movie was "Miracle on 34th Street" (and still is, to me). Now they might show it once a year!