Bill Gates wasn't born a great programmer and businessman. He was born smart and into a situation where he had access to a computer and then he worked his butt off to learn. Similarly, great athletes are both talented and work like crazy to hone their craft.
The point I took from the book is that hard work and many, many hours of study and/or practice is essential in order to get to the top of a field. Doing the hard work will not automatically get you to the top since at some point lack of talent or lack of resources may get in the way. But, you need to do the hard work in order to give yourself a chance to make it to the top.