Final answer:
The references provided do not contain information about why Essie Mae stopped drinking the milk she earned, as they do not pertain to her circumstances.
Step-by-step explanation:
The question asks why Essie Mae stopped drinking the milk she earned by sweeping an old white woman's porch for seventy-five cents and two gallons of clabber milk per week. Unfortunately, the provided reference materials do not contain specific information regarding Essie Mae or her circumstances related to the milk. The given texts do not seem to directly relate to Essie Mae's story or explain the reason behind her choice to stop drinking the milk. The materials discuss various themes of working-class struggles, economic hardship, social status, and the harsh realities faced by those with limited economic opportunities, but do not give a definitive answer to the question about Essie Mae and her milk.