Here's why:
* Clarity: Lowercase letters are easier to read and distinguish, especially when working with complex rhyme schemes.
* Convention: It's a long-standing convention in poetry analysis to use lowercase letters for rhyme schemes.
* Distinction: Uppercase letters are often used to represent other elements within a poem, such as stanzas or line breaks.
For example, a simple AABB rhyme scheme would be represented as:
* A A B B
This makes it clear that the first and second lines rhyme, and the third and fourth lines rhyme.