Family structure has undergone a drastic change in past few decades. Earlier families were more close knit due to the joint family system. Differences and conflicts prevailed, however, moving out of the family or going nuclear was not really a norm. Now nuclear families are more predominant because of variety of reasons.
Families have moved apart due to reasons like employment, better prospects in other cities, need to get away from the routine and still life in traditional homes, need for more privacy, assertion of individual rights and choice, need to break away from family and be more independent in making choices in life etc.
Nuclear family is also a boon for many women as it has relieved them from the many responsibilities and pressures that the joint family could have. Caring for all the members, little space for asserting her thoughts and voice, being under scrutiny of elders and patriarchal male members, little privacy, interference in her personal life or pressure to bear children etc can take a heavy physical and emotional toll on women.
Having people with wide age gap, traditional, rigid or narrow-minded beliefs, different opinion, individuality, thoughts etc can make compatibility a big issue. Nuclear family could be a breakthrough solution to reduce family politics, tension, friction due to domination by elder members, patriarchy etc which many a times percolates into the marital life and may lead to marital discord too.
A decision to move away could be seen as hostility, but in reality it may just be a good way to not embitter the relationship further. Going nuclear does not mean that you want to totally abandon the relationships. It may just give both the parties space to assert their choices and reduce the tension that could arise out of so many differences. Besides, a little bit of distance and lesser intrusion may help in long-term sustenance of relationships.