It is said that photography should have a theme and a clean background, but why are some messy photography sweeping the street?

Style reasons. Street sweeping photography takes streets and cities as its theme, and shows the multicultural life of the city by capturing moments, people and scenes in daily life. The background of street sweeping photography can be messy, so that the audience can feel the feelings and thoughts that the photographer wants to express. Photography refers to the process of recording images with some special equipment.