Who actually still does this? When I was in college, around 20 or so, sure, it was normal. Now, as an adult, with a family and plenty of random yet necessary shit to do, I would be pretty pissed if someone showed up because they "felt like it". Nor would I ever think to visit anyone without making sure it was OK with them first.

Its hard anywhere to make good friends as an adult, I think. Work and existing personal relationships and responsibilities take up so much time that having any left over to establish new friendships is a luxury. Not to mention, would you want to "invest" that limited time in establishing a friendship with someone who's probably going to be leaving the country in a year or two?