Norah we are talking families here. Would you separate a parent from their young children for 2 or 3 years because they are studying for a degree?
Not every overseas student can afford to fly home every vacation, or even once in a year. I have met a number of students, especially from poorer countries, who come here at the start of their degree and do not go home until it is complete. When parents are paying for their children's education, they can often only afford to educate one at a time, so younger children may be in their late 20s before they get their turn.
Your daughter was not married with children when she went to to the US. Would she have been happy to leave a child under 5 at home with father and grandparents while she studied overseas for a year?
People in forces are away, often, what about them?
People train. People have off-site jobs for extended periods
She liked Cambridge, loved coming home. Not all schooling programs take 2 or 3 years, if one gets on with it, finishes fast.