I don't think the decline of unannounced visits is really that big a reflection of a decline in society. It's just that now because communication is so easy and straightforward that you just drop someone a text or quick call to see if their in before you pop over. So in my case it isn't that I see less of friends and family, it's just that they always give a heads up before they pop over such as "stick the kettle on".
Plus, given that in many cases you no longer live within walking "popping over" distance, you want to check someone is in before get in the car and possibly waste a trip.
Once I've had my dinner, cleaned up a bit, put the baby to bed, those last few hours before bed are my only time to relax. Even if I'm to just answer and dismiss the cold caller, it's breaking up the few hours in a weekday I get to just switch off. So I'm happier to just let them knock, hopefully it's raining, cold, windy and miserable and this odious virus of the modern world of hassling people in their homes come down with some debilitating pestilence.