Because you should have a solid understanding of how basic genetics work before you jump in head first and get over your head. Remember as a breeder, you are essentially playing God and are creating life. There are a lot of genes that react favorably with each other and some that don't so taking the time to educate yourself on the various genes and how to properly incubate and what happens if there are hiccups along the way are fundamental in this hobby.
You need to be responsible with these animals just as if you were to bring a child into the world.
Here is a good place to start http://ball-pythons.net/forums/showt...Basic-Genetics