Here's why:
* Scout is young and innocent: She's still learning about the complexities of life and the world around her. The biscuit represents something simple and familiar, but her description of it as tasting like cotton shows that she's struggling to grasp the nuances of her environment.
* The South is changing: The novel is set in the 1930s during a period of great social and economic change in the American South. The world Scout is experiencing is different from the one her elders knew, and she's trying to make sense of it.
* Race and prejudice: The novel explores the theme of racial prejudice and the impact it has on the community. Scout's description of the biscuit is symbolic of how her innocent understanding clashes with the harsh realities of racism and injustice.
* Symbolism of cotton: Cotton is a major crop in the South, often associated with hard labor and the exploitation of black people. Scout's description of the biscuit as tasting like cotton highlights the connection between her innocence and the harsh realities of the world around her.
In essence, the biscuit tasting like cotton is not a literal detail, but a literary device used by Harper Lee to explore the themes of innocence, ignorance, and the complexities of a changing world.