You know when I was a child, I really didn't give a crap that Santa didn't exist. My thought process was "as long as I'm getting presents, then my Christmas will be awesome." So I never understood why kids always got sad or depressed when they learned that Santa didn't exist and was just a relative giving presents.
Because the world is a little less magical, in a time when you still have the lack of responsibility to enjoy it. And maybe some kids think 'my parents lied to me' instead of what Apple Bloom comes to, which to be honest, is something I thought people would see as unrealistic.
I think it has to do with the excitement that awesome magical stuff like that would be real. I agree though, getting presents and having your home decorated with the LED lights and stuff was enough to make Christmas awesome.