Because their kids will learn more at Disneyland for a day than in their school.
Damn right! I turn my trips like Disney into science time. Once in a while, we discuss the "simple machines", sometimes it's hydraulics, and other times we discuss social sciences, crowd interaction, etc.
I hardly go anywhere with my babies that isn't more educational than a classroom. Even when we screw around at the beach or fishing, it's marine biology time. And when we get home, we look up all the questions I didn't know the answer to. We have fun, and we all learn lots.