@Nothing-above-Gronin Only because the story tends to stop halfway. People see a black guy in service to a white guy and think slavery, but the story as it goes back was that the zwarte piet figure was a child slave who was freed by Nicolaas, hence Saint Nicolaas being known as the 'friend of children.' Piet then became his knecht, which is an old Dutch term for assistant (which also means he was paid), and helped Saint Nicolaas spread joy to children.
@Vercalos That's another one, but that story actually surfaced later, and is ironically one of the more racist interpretations in origin. In 1947 an author suggested Zwarte Piet represented the devil, stained black by the soot of hell, who was chained by the Saint Nicolaas and forced to spread joy instead of misery for a brief time.