If we are to worship God alone, then we are not to worship graven images. While it may not be directly listed on a board as being part of the first, it is included in the explanation of the first commandment in the Catechism of the Catholic Church . To have a second commandment banning graven images would be a mere reiteration of a portion of the first. To make up for the added commandment, Protestants often combine the Catholic numbers 9 and 10 into one. The separation of the two also demonstrates the Church's emphasis upon the sacrament of marriage.
Divorce remains a serious sin.
To desire another man's wife is to desire to disturb a covenant made by two individuals in front of God.