Chessmasters are made, not born. Why not good programmers?
I'll answer your question with another question. If chess is analogous to programming, why can't computers write code as well as they play chess?
Human grandmasters are barely holding their own against chess programs these days. And depending on who you ask, human chess players have already lost the war.
The answer, of course, is that programming has an infinity of choices compared to chess. As others have commented, it's so open ended that it's more analogous to art, or writing, or other purely creative activities.
Also, just to clarify, I never said that you can't improve as a programmer. Sure you can. But 90% of the improvements will be realized in the first four years of your professional career, and the rest will be incremental.