I used to die of embarrassment when my folks would 'go for a drive' and drop in on someone. My dad's excuse was that he didn't want the people to 'to to any trouble' just because we were stopping by. I thought it was rude.
Now, I welcome folks who drop in on me. My house is open to friends. if I have to leave for something I can't put off util later, I tell them how long we have to visit. otherwise, I put on the coffee or get out the wine, and we have a good chat.