Question: Why is it that whenever witnesses are required in Islam, two women are required to take the place of only one man?

The Quran in Sura 2:282 says:

> 
> And let two men from among you bear witness to all such documents
>  [contracts of loans without interest]. But if two men be not
>  available, there should be one man and two women to bear witness so
>  that if one of the women forgets (anything), the other may remind her.
> 
> 
>

Answer: 
Firstly this is only, as the Quran points out, in the area of business contracts. Where if two men are not brought then 1 man and two women. The Quran also points out that this is in regards to the issue of forgetfulness, because the business world isn't the natural place for a women, the women's responsibility lies in taking care of her children and her home, where it is them man's job to go out and work to support the family. Furthermore as already mentioned two women in regards to business contracts, where if a women in an area of her expertise is to give witness then that witness is sufficient.
Quran itself states the reason clearly: "if one of the women forgets (anything), the other may remind her". This is about the way human mind works. Men keep the event in more details. This is about nature and something like a man being physically stronger than a woman. Allah that created human knows it better than any authority. So Quran have to be obeyed and a Muslim should not put questions on words of Allah. Interpretation of all cases is not so simple. We can not disobey a command while we could not find a reason for it.