The mahr (dowry) is something that is paid by the man to his wife. It is paid to the wife and to her only as an honor and a respect given to her and to show that he has a serious desire to marry her and is not simply entering into the marriage contract without any sense of responsibility and obligation or effort on his part.
And give the women their dowries with a good heart..." [Noble Quran 4:4]

This verse is addressed to either the husbands or the guardians. It is addressed to the husbands because it is their responsibility to pay the dowry. It could also be addressed to the guardians, not because they have to pay the dowry, but because in pre-Islamic jahiliya (and in much of today's "post-Islamic" jahiliya), they used to take the dowry of the women and not give it to them. This verse shows that the dowry must be given to the women and not kept by the guardians. The following verses also shows the obligatory nature of paying the dowry to the women:

First of all why the hell u want one of them to pay the other ? Is it a business transaction ? I pity u.

It is because the money is like safety to woman and she can use it when the man dies etc. or divorces.mehar will help women live until she fends for herself
Men are the protectors and maintainers of women, because Allah has given the one more strength than the other, and because they support them from their means.