Alex, that's a generalization. I got this from Wikipedia, I've read this explanation before at other sources;
Quote:
Sinterklaas is assisted by many mischievous helpers with black faces and colourful outfits, modelled after 16th century Spanish clothing. These helpers are called Zwarte Pieten (Black Petes) in Dutch (see below for names in other languages). During the Middle Ages, Zwarte Piet was a name for the devil. Having triumphed over evil, it was said that on Saint Nicholas' eve, the devil was shackled and made his slave. Although the character of Black Pete later came to acquire racial connotations, his origins were in the devil figure. This racialisation is reflected in the reworking of the characters' mythos. From about 1850, Pete was said to be an imported African servant of Saint Nicholas. Today however, a more politically correct explanation is given: Pete's face is said to be "black from soot" (as Pete has to climb down chimneys to deliver his gifts). Nevertheless, the tradition has been accused of being racist, and attempts have been made to introduce Gekleurde Pieten (Coloured Petes), who are coloured blue, red, etc., instead of black. This phenomenon of "Coloured Petes" was introduced nationally in 2006. The explanation given for this was that "Sinterklaas passed through a rainbow with his boat".[2] This effort was widely criticized in the media.[citation needed]
Traditionally Saint Nicholas only had one helper, whose name varied wildly. "Piet" or "Pieter", the name in use now, can be traced back to a book from 1891[3]. The idea that Sinterklaas has not one but many helpers was introduced by Canadian soldiers who had liberated the Netherlands during World War II and helped organise the first post-war Sinterklaas celebration.[citation needed]
In other regions where Sinterklaas is celebrated, like southern Belgium or Northern France, Saint Nicholas has different companions.