My point was that there are leading roles - lots of them - which are not based on classical physical types, more on personality, and the components that go into determining type may not be 90 percent physical, 10 percent personality. Willum Defoe plays a really menacing villain while standing about 5-8 (his program height may be listed at 5-10, but I have stood next to him in an airport security line and he looked barely 5-8).
Also, Brent Spiner played an almost 6 ft tall John Adams, so casting directors do not generally worry a whole lot about historical accuracy (other than for maybe George Washington and Abraham Lincoln).