The Store dominates the first half of the novel. It's where the workers of the community gather every day and where people come to pass the time. When everyone needs to listen to that famous boxing match, they all crowd into the Store. Where else would they go?
Momma's store is the heart of the community ("[o]ver the years it became the lay center of activities in town" [1.7]), and it helps the people of Stamps survive even through the Great Depression.
The idea of community, particularly black community, is very important to Maya's youth—it gives order to the world around her. The Store is the physical manifestation of that community.