I have a knack for picking dates when there are record heat waves so I often find I want extra ventilation, besides it is nice sleeping in the open or barring that just having mesh over you. It is more likely in some areas than others, but I have often had weather I felt was reliable enough to do so on many nights on my trips in much of the American west. It the east it tends to be a little less frequent, but even there I still manage to do so some of the time.

We are talking about campground campsites, but another time where I have often done the no fly or no tarp thing was in picnic pavilions, gazebos, and other improvised camps that are under a roof, but bug protection is still needed.