Because
Exodus 20:12
Honour thy father and thy mother: that thy days may be long upon the land which the LORD thy God giveth thee.
Deuteronomy 5:16
Honour thy father and thy mother, as the LORD thy God hath commanded thee; that thy days may be prolonged, and that it may go well with thee, in the land which the LORD thy God giveth thee.
Ephesians 6:1-3
1
Children, obey your parents in the Lord: for this is right.
2
Honour thy father and mother; (which is the first commandment with promise;)
3
That it may be well with thee, and thou mayest live long on the earth.