So players who are taller tend to do better in these sports, all else being equal, just as heavier players do better in football. This means that most high-level players of these sports will be taller and heavier than the average person. Of course, an exceptionally talented "short" person (especially one with a big vertical jump) can also make it in basketball or volleyball. Spud Webb, who holds the NBA record for vertical jump at 44 inches, is only 5 feet 7 inches tall! And there are still professional football players (usually defensive backs, quarterbacks or wide receivers) who weigh less than 200 pounds but are exceptionally strong and fast for their size.

The other reason we have such tall people in basketball/volleyball (and such huge people in football) has to do with the fact that the average size of the U.S. population has increased dramatically in the past 50-100 years. This is a function of better nutrition (and, especially in football and bodybuilding but also in other sports, partly due to the use of anabolic steroids). With a larger average, the very largest people will also be larger than they used to be.