Not sure what kind of answer you are looking for?? Your thread title is a bit inflammatory...
Jockeys use whips to increase forward motion, encouraging the horse to move out. Kicking or leg pressure isn't much of an option, partially because of the rider position that jockeys adopt to maximize the horse's speed and freedom of movement. Another reason that the whip is used, rather than leg pressure, kicking, or spurs, is that those forms of pressure cause the horse to suck in his barrel and shorten his stride - not at all the goal of a race.
... not sure what you are looking for either... but you do now that the horses are not being whipped to death during a race!!!they only have a certain amount of times to use it. In the USA I think its 20 - 30 times!?!?! And you will notice its generally in the beginning to get a good spot and in the end to encourage longer strides and to let loose.
And as the post before me stated its there sign/cue instead of leg pressure.legs down on the side of the horse hurts the dynamics of this event and makes it difficult for the horse to run freely. For them its a different aid/cue to listen to.
And it can't hurt them the few times they use it in a race or for practice. Horses kick each other harder than any human can use one of those when riding.
To much whipping is excessive and can cause damage eventually. But used right its very effective to communicating with the horse when your practically in the air going a distance at full speed with limited body connect with the animal
There are a lot of different reasons to use a whip during a race, encouraging a horse forward is only one of them, and not all horses respond well to that cue. Jockeys spend a lot of time practicing fancy whip work as defensive move - fanning your whip (not actually striking your horse) on the horse's off side keeps another horse off of you and will prevent another tentative horse from passing. Fanning the whip can also keep your horse from bearing wide on a turn; tapping the whip on the off shoulder or fanning in front of the horse's eye can be used to signal a lead change.
So while you may see a lot of whip movement during a race, a lot of it isn't actually striking the horse. And as another poster mentioned, excessive use of the whip (actually striking the horse) will be penalized
I'm pretty sure a whip ban came in to the UK a couple of weeks ago about striking the horse, and where I'm not an expert I agree, I have never see whip marks on a race horse when they've finished, where as my own dressage horse (before selling) had a couple of welts on his rear end when bucking and general misbehaviours became apparent....
There's now a set limit of number of times you can use the whip during a race in the UK. I think it's 5 in Flat racing, 7 in Jump racing and the whip can only be used a maximum of 5 times during the final furlong.