Disney is classic, that's why. We grew up on Disney, our parents grew up on Disney, and probably their parents grew up on it too if said grandparents are young enough (ex: my grandfather was born sometime in the 1940s, I believe, and Snow White came out in that same decade). It's something you hear that everyone, and I mean everyone, can relate to easily and go "Oh yeah I remember watcing <such and such Disney movie> when I was a kid!" It's endearing, ontop of all of that.
Pokemon, on the other hand, doesn't have the same classic feel or "tag" to it as Disney does. Not everyone can relate to Pokemon like they can to Disney. It came out during my generation and hasn't been around as long as good o' Mickey Mouse has and thus hasn't had any chances to really bridge any kind of generation gap/stigma. Just the other day, my mom picked up my Mismagius plushie and remarked, "Where is your brain...?" If this were a Disney character instead, however, she'd understand better since she grew up on Disney like I did (and she worked at Disneyland as a teen, ontop of it all).
... Okay, so I'm shooting in the dark here with this, but that answer made the most sense to me. >: