I'd speculate that the 10,000 hour rule is a product of an American obsession with the idea of hard work being the most important factor in success, with the idea that everyone's abilities are reasonably equal, and determination and diligence is what differentiates them. This satisfies a certain sense of fairness and justice in life. I also think it's just not true, more the product of wishful thinking than any evidence.

People have differing levels of talent in different areas, and this does have significant effects on success and ability. There are "super-brilliant slackers," and there are very hard working failures. Talent, too, does not necessarily correspond with interest and enjoyment. None of this is fair, but life is not inherently fair.

The important thing here, more than practice, is figuring out what one is good at doing, and what one enjoys doing, and coming up with things that are in both sets.