Squash Balls are Unique
At room temperature, squash balls barely bounce. When they get hot, and bounce a lot. From out of the box to hot during play, the bounce of a squash ball can as much as double. No other ball in any other sport is like this.
This big range of bounce greatly affects the game. If you can't get the ball hot, you get a low bounce. If you can't get the ball warm, you get a dead bounce.
Most squash players in the US use the Dunlop Pro (double yellow dot) squash ball. However, only the top players can get this ball hot. Most club players can not, and they get a low or dead bounce.
Squash ball companies know about this problem, and because of it, they make a different balls for different skill levels. By using the right ball, all players can get a normal bounce.
A Graphic Example
Below is a picture which shows how the bounce of a Dunlop Pro changes as it gets hotter. (Several drives were filmed with a video camera, and the flight paths were overlaid onto one picture.)
Top players get a bounce like the black line. Most club players get a bounce like the red or blue line. This picture shows just one bounce. The difference during play is much larger, because there is less rebound on every bounce. (For more information, see Balls, Bounce, and Surface Temperature.)
The lower the ball temperature, the lower the bounce. The lower the bounce, the more the game of squash changes, and the game often changes dramatically.
Softball, Lowball, Deadball
Most club players might think they are playing the same game as the top players, but in fact, they are playing a variant. Instead of playing softball squash, they are playing lowball squash or deadball squash.
In tennis, to get this same result, you would give normal tennis balls to top players, and everyone else would use a tennis ball with a hole in it. The lower the skill level, the bigger the hole in the ball.
Sound ridiculous? Well, there is an entrenched tradition in squash that insists on the equivalent of just that, and it is called "You should use the Dunlop Pro, even if you are not a top player".
The consequence of this is that softball squash (a normal bounce) is reserved only for top players. Everyone else, who are the vast majority of club players, play lowball or deadball squash (a low or dead bounce).
The Solution
The solution is simple. Ball companies already make a line of balls for different skill levels. All you have to do is select the right ball.