A very simplified, but scientifical nonetheless, explanation ( to some extent i work in the field and yes, i have a official piece of paper that says that, but i don't want to use it to sound more authoritative):
Shmups are a mix of a physical and intellectual practice. You may actually have a slight advantage than others in hand-eye coordination, but once we speak of incredibly complex tasks like one-lifing DOJ, you need to practice in order to learn the optimal (in the sense of the best) route to do that. If that route consists of 1 million movements, you need to learn them, pretty obvious: some people will learn them 10 at time, some 9, some 11, etc. This considerations are based on one simple principle, that you know what you-re doing and thus are able to correct yourself when not learning the right sequence (and also to find out the right sequence). This means that no, you have to think and solve the problem.
Once you know how to solve the problem, you compress it to a simpler form and once you do it one zillion times, it becomes like breathing, i.e. a mechanical cycli function stored in the cerebellum. Of course, if you learnt the wrong route and you've stored in your cerebellum in a compressed way, you will have an hard time to correct yourself (think of learning to walk in an unproper way and unlearn it to do it right).
Final point is the motivational issue: anything can be learnt, if you like what you're doing, you will probably go faster (and in this case, a talented person that faster by going at 11, will probably gear up at 12). If you hate it, you may slow down your learning speed. Finally, if you live in a place where everyone does a given thing, you can easily understand how to get the whole process in the right order, so you can virtually become good as the the best one around, just at a slower pace. In some exceptional cases (running 100 mts in les than 10", one-lifing DOJ with flawless combos), you may simply not be good enough, in the sense that it will take you forever. Those are exceptional cases.
One note on japanese culture: the ninja players around are all very talented, but they're also people that spend hundred of hours in practice, and in understanding all the subtle nuances of a game. It is true that, if you grow up in japanese culture, being extremely focused on what you do is the norm, so hundred of hours in something you like are actually the norm.
Add in that it's a pretty competitive culture and that being the best one at anything is worth of respect, and you've covered the social aspect.
Of course, a number of bizarre, irrational or simply non-sensical replies will follow, after all inferential reasoning seems to be lacking in some of the nice peeps posting here

"The only desire the Culture could not satisfy from within itself was one common to both the descendants of its original human stock and the machines [...]: the urge not to feel useless."
I.M. Banks, "Consider Phlebas" (1988: 43).