Q48. "Can you tell me why the ERA was not ratified?"
A. The ERA was not ratified because not enough states approved it before the deadline set in the legislation, nor in the extension given it by subsequent legislation.
As for the reasons it did not pass in certain state legislatures, you'll have to refer to the archives in the various states to find out the arguments for and against. The general argument against it, however, was that the ERA would burden government and business too heavily; that men and women are inherently different, and those differences should be celebrated and not suppressed; and that it simply was not needed.