A cultural problem
The idea of separate life/location for youngsters, especially after marriage, from parents is actually justified. Unlike old days, now youngsters are in a need to perform independently in order to be successful in their career. They need a freedom of mind, with due apologies presence of parents in the same house actually interferes with the freedom of mind for the young generation. This is mainly because of generation difference and youngsters are forced to be conscious about their parents. Parents are generally outdated with their expectations/behavior and our adjustments to them may not be relevant to our times. This is particularly true if one decides to spend his/her entire lifetime with parents. Although it is our responsibility to spend time with them but in reality spending time with them cannot be considered quality time with respect to the youngsters' prospects or growth in present times. Youngsters will always strive to stick to the culture as much as possible and be responsible in every way parents expect them to be at the same time they need some space in order to lead a life with freedom of mind so that it will be easy for them to achieve better in this competitive world.
The youngsters' family have their own way of leading family life that they need privacy in all aspects of life without worrying much about the presence of parents. Let me be frank, even sexual relationship is kind of awkward in a joint family setup. This is one such example and there are many aspects of life that are private and passionate for youngsters. Unlike those days, nowadays profession is more inline with passion and it is important we lead a life full of passion in order to be successful. Passion is not something you switch it on or off at different times. With such a joint family system, life is actually a disaster for both son and daughter-in-law. Parents who are well aware of the culture, values and responsibilities should understand that the youngsters are also adults they are also well aware of their responsibilities. It is important they trust their children. Even two houses next door or two adjacent apartments should do good at least there should be a wall between two families and not necessary for the children to move away to a distant location.
Unfortunately it is not applicable for many families who cannot afford / rent a second home, in that case we should be able to appreciate their joint family system after all every one of us are originally from such a system. Also it is not applicable to the people who are in the religion (like archakas and others) and are not typically materialistic, for them joint family system is recommended and absolutely justified.