This is a Ancient Hindu tradition where the Hindus have a concept of "Kanya Daan" wich means "Donate the maiden", where the father "donates" away his daughter to her husband and charges him for her well being.
The image is that of the parents "donating" their daughter to the Bridegroom.
Once you have donated away anything, one cannot make use of it in any way because that will be against Dharma.
This also means the father cannot claim back the daughter, because she becomes member of a different family and clan.
That is why in Hindu society, the women did not get part of her fathers property, since she was no longer his daughter after marriage. She got her share of the property during marriage.
This is why when the bride's family visit the Bridegroom they do not accept anything in return, because if they accept anything it will be in "Exchange" for the bride and will thus put a Price on the girl and negate the concept of "donation" or "give away".
This includes drinking water from the Bridegrooms house.
I suspect the pakistani's have forgotten their hindu roots, but still follow the customs without understanding the importance of what they are doing.
