Why should flour be sieved?

The first is to filter out the impurities in the flour, because the flour will be ground unevenly during processing, and the larger wheat bran particles can be filtered out. Moreover, when flour is stored, it is stored in piles. There is moisture in the air. When flour absorbs water, it will form flour dough. When making a cake, it is not easy to mix it evenly in the batter. Sieving can make flour fluffy. Moreover, sieving can make the materials in the formula mix more evenly, such as adding matcha powder or cocoa powder to the formula.