For this cause ought the woman to have power on her head because of the angels. Nevertheless neither is the man without the woman, neither the woman without the man, in the Lord. For as the woman is of the man, even so is the man also by the woman; but all things of God. Judge in yourselves: is it comely that a woman pray unto God uncovered? Doth not even nature itself teach you, that, if a man have long hair, it is a shame unto him? But if a woman have long hair, it is a glory to her: for her hair is given her for a covering. (
1 Corinthians 11:10-15 KJV)
The uncut hair of a woman was given by God as a covering. Those who advocate the veil are advocating as belief that something man made can supercede something God gave as acceptable as a covering. God instituted what the covering was to be on a woman, and that covering is uncut hair.