Bubbles,
I think our DDs are at the same University, which perhaps illustrates how different, different experiences can be. DD unlike her brother, has opted for University away from home (actually she did not get a place at our local one, which to some extent she regrets - first year in halls were grim.) Her best friend, for family reasons goes home every weekend, and she is far from the only one. It seems very normal to go home three or four times a term at least. The exceptions being those who live too far away, or those who were at boarding school, who lack home networks, but since they tend to arrive at University in large friendship groups, their experience tends to be different anyway.
If your DD had been at University a few years back before fees started to bite, it would have been different. But as far as I can see, things are different now. Some students, and their parents, want to keep debt to a minimum so living at home becomes more attractive. Though in fairness this does not apply to a number who attend our DDs University, where really money does not seem to matter. Some really have extraordinary amounts, so are hard to mix anyway, especially if you are not part of the posh 21st birthday party etc, network.
FWIW I have not heard of students holding dinner parties. A trip to ‘spoons perhaps, using vouchers filched from freshers week. But then there is no reason why students living at home cannot join them.