In anthem why is equality asigned to the home of the street sweepers?

Simple answer: The Council of Vocations assigned him to this position.

Additionally: Equality would have been considered a troubled youth, for he fought with his brothers, asked unanswerable questions, and committed transgressions of preference. Certainly, the society and its Councils would have deemed him a delinquent, and it is possible that this position was assigned to him as a punishment and a means of keeping him out of places where he could cause trouble. When he is sweeping a road between agricultural fields, it is difficult to pose a ruckus.