Equality 7-2521 gets the job of "street sweeper" for no other reason than that is what is selected for him by the Council of Vocations. When he went to find out his fate, he was hoping to be named a scholar. This wish was a sin in the society. That is why, when Equality 7-2521 learns of his fate, he says he is happy:
We felt the cords of our neck grow tight as our head rose higher to look upon the faces of the Council, and we were happy. We knew we had been guilty, but now we had a way to atone for it.
The society has trained him to be happy about whatever fate he receives. He must portray a sense of happiness outwardly, but he also is a little happy on the inside because of his conditioning. If the society allowed its citizens to be involved in the selection of their vocations, it would fail miserably.