Sometimes the friend/family exposure is dictated by where and when you're there. Sometimes the “choice” of background and light is made, in part, to keep a famous background in the photo, to say, “We were there.”
Sometimes you can choose the time of day your photographing, the background, and the way your traveling companions are facing, thereby control how light illuminates your subjects but more often, locations and schedules dictate exposure details.
The place and time for portraits of local inhabitants is rarely in the traveler's control, but the photographer can often control their position to help set up the portrait.