In 1940, Hattie McDaniel became the first black woman to be nominated for, and win, an Oscar. She got her best supporting actress award by playing Mammy, the jolly house slave in Gone With the Wind. At the ceremony, she was not seated with the rest of the cast; instead she and her guest sat at a segregated table.

The award was bittersweet for black audiences. The role required her to be spoken down to by a much younger southern woman (Vivien Leigh) and didn't touch on her life beyond her white owner's house. Since then, only five black women have gone on to win acting Oscars. That became six after Octavia Spencer won on Sunday. Her role? A maid in the 1960s.

The nomination of Spencer – and Viola Davis – for their performances in The Help had been controversial. The film and the book on which it is based caused the Association of Black Woman Historians to release a statement saying that "The Help's representation of these women is a disappointing resurrection of Mammy … the caricature allowed mainstream America to ignore the systemic racism that bound black women to back-breaking, low-paying jobs where employers routinely exploited them."

Blogs debated the stagnation in the roles for black actresses, and comments such as "I want them to win, but I wish it wasn't for this movie" abounded. The criticism fell on Davis and Spencer too. To Essence magazine, Davis said: "Of course I had trepidations. Why do I have to play the mammy? But what do you do as an actor if one of the most multi-faceted and rich roles you've ever been given is a maid in 1962 Mississippi?"

This is a pertinent question. Why is the variety of roles available still so limited? This week, Davis asked: "Do you know the black equivalent of a Meryl Streep? Or a Julia Roberts or a Nicole Kidman?" And why does the Academy fall over itself to reward these "degrading" performances with awards?

In real life, McDaniel had been a domestic worker, often in the gaps between acting work. She reportedly said: "Why should I complain about making $700 a week playing a maid? If I didn't, I'd be making $7 a week being one."