It's midnight, and after a few bottles of wine your guests head to the guest bedroom. Well, "guest bedroom" is putting a positive spin on "our junk room that we cleaned up before you got here because it has a fold-out sofa bed."
Cue the guilt next morning as your guests limp out of their bedroom, avoiding your gaze with their fatigued eyes as they tell you through clenched teeth how great a sleep they had. You could have installed a full-size bed in there, but you also need the floor space.