Spontaneous visitors make some people feel self-conscious about the state of their house or standard of dress. One person thought it was all about timing: evidently Saturday afternoon is fine but 7pm Tuesday not so much. Another commenter suggested the need for a drop-in App that could tell your circle of friends whether you're available or unavailable for drop-ins. This idea harks back to the Victorian tradition of householders having designated times for receiving visitors.
The writer of The Surprise Visit. Don't. Please is unequivocal on the subject: "There are no excuses for not contacting the person before just lobbing on their doorstep." After all, the resident you're about to disturb may be unwell, already hosting visitors, poised to go out or simply enjoying the solitude.
For the record, I'm one of those people who consider the drop-in to be anything but friendly. If I'm not given notice I may well be sporting a) pyjamas, b) facemask, c) just washed hair, d) a bad attitude or e) all of the above. In fact, I'm unlikely to answer the door if I'm not expecting someone - which may sound unfriendly but it's not nearly as hostile as the commenter who confessed: "I don't answer the doorbell if I AM expecting somebody." Now that's what I call antisocial.
Are reports of the demise of the friendly drop-in true? Are drop-ins acceptable in your circle of friends or should prior appointments be made? If you're someone who is inclined to drop in unannounced, what precisely is your aversion to calling ahead?