This does not mean there are no tall point guards in the NBA. If you need any proof, players like Steph Curry at 6′ 3″ and Damian Lillard at 6′ 2″ are legendary point guards despite being shorter than the average NBA player. This is because ball-handling skills and game IQ play a bigger role in this position than height advantage.
However, among all the positions in the NBA, the point guard has always been the shortest position. Height and wingspan are some of the physical characteristics that NBA scouts look for.