Why is 5'7" considered short and 5'10" tall when the difference is only 3 inches?
because somewhere you draw the line and make the separation. it does not matter where you draw it because there alway will be people complaining. why i am in this side of the nine and not in the other.
So lets say we but the line at 6 then someone 5 11 complains its only 1 i should be consider also. So we lower. Guess what now we have the 5 10 complain. And so on and so on.
Usually those things are back up from statistic. So we find out the average height in this case of a man. So we choose a range of height as normal which will have the majority of the population in there and then above that range they will be consider tall.
This line is not static but follows up the trends of the people. In the last century because of the more meat in the diet in many countries the average height has risen and thus the height you need to be considered tall.