In general life we bow to people we respect and worship, but God makes people bow for different reason. Of course we shall worship God and adore, but sacred meaning of bowing is not only expressing respect.
When a person stands on his knees, he deflects legs. In Russian there is an expression: there is no truth in legs. In legs all the sins cave in. When person stands on his knees, he opens heart to God and He watches which sins person did by himself or by destiny. Destiny is scenario or program of God. When heart is pure, even though person was a sinner, soul goes to heaven.
When person bows down to God, he connects mind to Gods feet. We gratify God, we please Him and we give thanks when we bow.