When you are a single student, or couple with no kids, or single working professional, your priorities in life is different. As kaji_sahab rightly said in earlier post, 'as time changes, priorities change too.' I found the following points in some article online.

Lack of support system:
Not every immigrant can cope with life in a foreign land without the support of family and friends. Relocation is a life-changing experience, especially when kids come into the picture. "It makes a couple vulnerable to either getting totally involved in their respective duties not wanting to bother the other partner, or them feeling very lonely and depressed,” says Mary John, consultant psychologist. The problem could get aggravated when the partner is the only support system. “We can’t expect our partner to be our partner, husband/wife, boyfriend/girlfriend, best friend, mother, father, etc. This often leads to unrealistic expectations, which inevitably lead to disappointment and often heartbreak,” says Dr Lavina.

Loss of job especially if you are NOT a GC or Citizen:
A job loss will tear apart a family anywhere in the world, but more so in the US where it impacts survival for immigrants as it is directly linked to employment visa. Your employer has control over your destiny to get a GC. You not only have to worry about getting laid-off due to company re-organization, downsizing, or funding cuts, but your main fear is staying in status all the time until you secure GC.

Child rearing issues:
In the absence of a family support system, many working couples struggle to share responsibilities when they have children. This strain often drives a wedge in career oriented parents, resulting in separation.