I am not from Islamic religion, so don't have any deep knowledge on you r rules. Please forgive if I hurt someones sentiments. I don't mean that.
My belief is that in all religions whether Hindu, Islam, Christianity....people heavily depend on words written in scriptures, Quran, Bible. They don't understand the situation in which the rules were created and decisions were made. They only want to follow everything written millions of years ago, word to word. And thats where most problem happens.
Men question women's character and ask her to give proof/agnipariksha. Why only because in Ramayan God asked a woman to do so. They don't understand the reason why God did what he did and that leads to backward society.
I think Hina mentioned that earlier second marriage was to let widows/orphans have a chance of family. But people now uses same excuse to fulfill their dirty motives.