Perhaps the filmmakers are afraid of confusing the viewer with another unstable, violent, confusing female authority figure. Perhaps it is the demented songs that seem to promote child abuse (although who can resist joining in with the chorus of "Wow! wow! wow!"?)
Speak roughly to your little boy,
And beat him when he sneezes;
He only does it to annoy,
Because he knows it teases.
Wow! wow! wow!
One of John Tenniel's original illustrations of the Duchess from Alice's Adventures in Wonderland
The Duchess was the first boss in American McGee's Alice PC game. If she catches up with you, she gnaws on your head in a gruesome way. When she is defeated, she sneezes her own head off.