Book of Deuteronomy Foreignness and the Other Quotes

How we cite our quotes: (Chapter:Verse)

Quote #10

"When you reap your harvest in your field and forget a sheaf in the field, you shall not go back to get it; it shall be left for the alien, the orphan, and the widow, so that the Lord your God may bless you in all your undertakings. When you beat your olive trees, do not strip what is left; it shall be for the alien, the orphan, and the widow. When you gather the grapes of your vineyard, do not glean what is left; it shall be for the alien, the orphan, and the widow. Remember that you were a slave in the land of Egypt; therefore I am commanding you to do this." (NRSV 24:19-22)

When thou cuttest down thine harvest in thy field, and hast forgot a sheaf in the field, thou shalt not go again to fetch it: it shall be for the stranger, for the fatherless, and for the widow: that the Lord thy God may bless thee in all the work of thine hands. When thou beatest thine olive tree, thou shalt not go over the boughs again: it shall be for the stranger, for the fatherless, and for the widow. When thou gatherest the grapes of thy vineyard, thou shalt not glean itafterward: it shall be for the stranger, for the fatherless, and for the widow. And thou shalt remember that thou wast a bondman in the land of Egypt: therefore I command thee to do this thing. (KJV 24:19-22)

Why do the writers of Deuteronomy use the figures of orphan and widow so often? Would we use the same examples today? What would be the equivalent in our society?