Why do Lou and the narrator want the painter lady to leave the wall on taliaferro street alone?

Lou and the narrator want the painter lady to leave the wall on Taliaferro Street alone because they value the wall's existing character and history. They see it as a canvas of personal memories and community identity, fearing that any alteration would erase the essence of what it represents. Moreover, they believe that the wall should remain untouched to preserve its authenticity and the stories it holds.