I think it's just the opposite. Allowing employers to ask wage history helps maintain the wage gap. If women are underpaid at their first job, then that will propagate forward to future offers. If they can't ask, then they'll have a harder time knowing whether they can continue to underpay a woman. Having a stated salary range also makes it a little harder for them to play games.
Ethics? Morals? Not knowing exactly what sort of lie they can get away with? Years of training and practice in not lying? Fear of getting caught and not getting the job? Fear of getting caught later and losing the job?
