Answer:
because she understands that society, at the time, valued only a woman's appearance and not her intelligence. She also wants her to be a "fool" so that she doesn't understand this cruel reality.
We can see it too in the attention paid to musical devices that are incorporated into the poem. Devices such as alliteration, assonance, and rhyme, for example.
A sacrifice, whether its an animal or something valuable.
<span>Group A
By Sinel's death I know I am Thane of Glamis;
But how of Cawdor? The Thane of Cawdor lives,
A prosperous gentleman; and to be King
Stands not within the prospect of belief,
No more than to be Cawdor.</span>
