Although it appears that the inheritance of men is twice that of women, a closer look reveals that from one viewpoint, the inheritance of women is twice that of men! This is due to Islam's support for the rights of women.
Islam has placed certain responsibilities upon men, because of which, virtually one-half of their earnings is spent upon women whereas no such responsibilities have been placed upon women.
The male has to bear the expenses for all of his wife's needs such as housing, clothing, food and other necessities; apart from this, the expenses of his minor children are also to be provided by him, whereas the wife is exempted from every kind of payment, even if it is for her own self. Thus, a woman can stockpile her entire share of inheritance, whereas a man is bound to spend his share upon himself, his wife and children. Consequently, half of his earnings are effectively spent upon his wife and the other half is for him, whereas the entire share of the wife remains unused and intact.
For a better understanding, consider the following example: Suppose that the entire wealth existing globally is 30 billion dollars, which will be gradually distributed as inheritance amongst men and women (sons and daughters). When we compute the earnings of all men and women of the world by way of inheritance, we find that of this amount, the share of the men is 20 billion dollars while that of the women is 10 billion.
However, as is customary, the women will marry, after which the responsibility of providing for their expenses will fall upon the shoulders of men and so, the women can conveniently put their 10 billion dollars aside while, at the same time, be a partner to the men in their share of 20 billion, since this amount would be utilized by the men to provide for the expenses of their wives and their children.
Thus, in reality, half of the share of the men - totaling 10 billion dollars - would be spent on the women. This, in addition to the 10 billion dollars, which the women had placed aside, would collectively amount to 20 billion dollars - two-thirds of the (supposed) global wealth - whereas the men, effectively, do not use up more than 10 billion dollars for themselves.
In conclusion, the actual share of women, with respect to 'consumption and use', is twice the actual share of men, and this distinction is influenced by the fact that, generally, their ability and strength for generating earnings is less than that of men. This is a kind of just and logical support, which Islam has offered to the women, allotting a greater actual share for them although, ostensibly, their share appears to be one half (that of the males). Islam is a just religion and worthy of following.