To answer the question, I guess the easiest answer as to why the ERA should finally be enacted is symbolic: it would enable the Constitution to reflect the principle that men and women are equal before the law, in the same way the 14th Amendment recognizes the principle that there is no master race. The consensus in our society now is such that any policy which discriminates based on sex, or any policy which has a clearly adverse impact on women, is going to be legally questionable, if only under the Equal Protection Clause, so "heightening the scrutiny" such laws will face following the enactment of the ERA won't make much difference. I can't believe this would be such a difficult decision for the Democrats, now that they control Congress.