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.
A guy (30-year-old photographer) who never really played golf before is trying to reach the PGA Tour through 10k hours and deliberate practice. (ie, Not just mindlessly spending time on the driving/putting range).
In the last four years he's practiced about 5500 hours and gone to a handicap of 3.3.
That would be 9 hours per day, every single day of those three years. How many people have even had just one day where they spent nine hours on the same thing? That's not including breaks, and periods where you mind wanders or you're not focused.
And it is supposed to be 10,000 hours of "deliberate practice", if I remember correctly, i.e. exercises and trials focusing on harder point, with an immediate feedback. I don't think it is possible to keep that kind of focus 9 hours a day for 3 years in a row.
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.