Re: I need to ask
It partially has to do with the flatness of the ball. A shorter player has more difficulty generating powerful topspin (Kuznetsova's forehand, for example) than powerful flat shots, but powerful flat shots have less of a margin for error. Take Henin's serve, for example. She hit her 2nd serve at a higher speed average than basically anyone on tour, but she didn't get very much action on it. She was physically limited in what kind of serve she could hit because of her height. She took the chance of hitting more double faults, which players of comparable height and lesser serves (Evert, Hingis) did not. As a result, short players either hit with (generally) lots of topspin but little pace (ASV, Coetzer) or hard, flat, and erratically (the others). Only a few true shorties (Henin, Evert) have managed to balance hitting with power and hitting with topspin in a way to keep the ball in play (topspin) without compromising control of the point (power).
Taller players can do a lot more with their serves as well, as I indicated earlier, and have better reach, which helps at the net. But, very few of the taller women are particularly quick, whereas there aren't many slow short players. Shorter players have slightly better balance on the average due to their center of gravity, but taller players can get to balls by virtue of being longer limbed. Also, on a couple surfaces, height is a huge help. Being in the 5'8''-6'0'' range is helpful on clay as the high bounces affect you less, while on grass, the two extremes are more beneficial as the tall players are that much tougher to break serve against while the shorter players are that much lower to the ground naturally.
Also, tall people can generally put on more muscle mass without dramatically hindering their movement. Long legs and arms give you more area to distribute the muscle to, which keeps you still lean enough to move unencumbered. Put the same amount of muscle weight on a shorty and they develop a slight waddling effect, like a bird.