I'm not so sure it's just flattery. For a few years I found myself doing an increasing number of specific-use commercial portraits and head shots. My rule of thumb was to ask intended use and then decide the angle. For example, a portrait of a doctor new to a practice and or marketing purposes I would use a slightly lower angle - whether for a man or a woman. This makes the presence somewhat more "commanding" and suggests competence and authority. On the other hand, if I were doing headshots for realtors, I would use a slightly higher angle because this suggests someone working for you as opposed to telling you - no-one wants an intimidating real-estate agent! Annual reports for financial advisors would require two approaches. The chief executive would need the commanding and in-control approach of the lower angle; whereas, for the day-to-day advisors and marketing people I would use a higher angle to make them appear more "approachable". The concept is similar to the executive who has his / her chair arranged higher than those of visitors. A lower camera angle suggests command and a higher camera angle suggests compliance.
In addition, a lower angle for men often minimizes a receding hairline, (or the "forehead on steroids" as I describe my own predicament) This is good, of course, for male stamp collectors - where "philately will get you everywhere" ::o:o (Really sorry guys........I just couldn't resist )