why do you think angelou included the part about her desire for pineapples? what does this convey to the reader?

I'm not sure this conveys a lot. Angelou displays her keen powers of description, as she tells of her love for chocolate Kisses, and the pineapple upside-down cakes that her Momma makes at Christmas. The descriptions are rich with sensory images, and are reminders of a child's joy at the little things in life.