Why isn’t it enough for me to live by my own personal values and morals?
The Seven Noahide laws are the laws that God gave to the world, in order for the world to be a civilized and peaceful place. If every person would make his own laws, according to his own intelligence, they would change according to the person’s maturity and changes in circumstances.
The world would be a jungle, each person living according to his/her changing values. God created the world and wrote a manual by which we need to live. Just as any electronic device company writes a manual for every device it sells.
God gave a manual for all the nations of the world. This is the code that never changes, since it is a Godly one.