why this happen ?

Well its just the nature of life. I dont say leaving our parents is wrong. Because the one whom we love and marry is gonna take up our parents position. And that is the only relation god given us the choice to select.

When a person gets married it says in Genesis 2:24 For this reason a man will leave his father and mother and be united to his wife, and they will become one flesh. This means that both of them are responsible now in their new life as husband and wife but that does not mean that they would forget their parents. I beg to disagree on what you said "leave the whole world", it sounds too selfish. You will only live a few blocks away or more, but in your heart, your parents will always be there as you love them the same. I got married and even if I was away geographically from my parents, it wasn't a problem because we always do talk online and I get to see them during my vacation. Same as to my in-laws. My husband does support his parents financially and we love them even if we do live far away from them. Meaning our responsibility is there even if we got married and lived separately from our folks.

Hi there Ashoknarwal! I guess it is part of the vows that we give when we got married that we will become one. I think that it comes naturally when you really love your partner and it doesn't need to be asked from each other. As for our parents, it should be clearly understood that we shouldn't turn our backs on them but we also have to start our own family and stand on our own feet. That time will also come to us when our child gets married and would have to start their own family too.