Two specific things that tend to stick out about Willie is that, a)  he starts out the play on his knees, which is a symbol of oppression, b) he seems to accept his position as servant being the one person who immediately refers to Hally as "Master", and c) in those pivotal moments when you, as a reader, feel like exploding and rage hits you, he seems to swallow it all up, and let it go.

For these reasons, what this reveals is that he is indeed subjugated to the unfair rules of apartheid, and he accepts his secondary position in society. He actually serves as an atmospheric element to the play, for he seems to represent the worst aspects of the situation (the emotional ups and downs, the lack of hope, the "getting used to it")- hence, his language, as well as his actions are that of a person who has no other choice but to accept what came for him without taking a stand.