Just because the class of people in the Mad Men universe are slowly becoming aware that black people exist in society, that doesn't mean that black people are just now appearing. The Civil Rights movement and the Women's Lib movement had closely related trajectories, yet from the very first season, we learned all about Peggy's backstory as she rose from secretary to copy writer (still rare at the time). Why is it so difficult to do something similar for a black character like Dawn? (And yes I know she got two whole lunch counter scenes
with another talking black character.) Betty had a black housekeeper, who was unceremoniously dumped. Why not learn about her life and how it intersected with the Draper family's? Why not follow up with Pete's idea of going after the black market for TV sales? Again, just dumped. Why not go ahead write about
the invisibility of black people (without whom neither the city nor the firm could function)? Instead, they only put black characters in the forefront for a hot second when there is a Very Special Race Moment, like "can Peggy trust Dawn not to steal her purse," or watching white people watching black people react to MLK's assassination.