I find it odd that in Squash championships, players don't put much energy into the serve. It seems to me that their serve is about half the speed of their fast shots during the game. Is there any rule preventing them from doing so? Or is there another disadvantage?
The problem with hard serves is that the ball bounces back too high and far from the back wall. This gives the returner too much space and allows them to either make a kill shot or put the server into a tough position right away.
Squash is a game where ball position is very important, often more so than power. A good squash serve hits high on the side wall and lands softly in the back corner so the returner must play a defensive shot.