Nor do I see 1,000,000 clones of Daniel Jackson sitting in rooms meditating to ascension.

One of the things I love about Naruto Shippuden is that there's an episode where Naruto (whose signature move creates shadow clones of himself) does precisely this. It's revealed in the episode that when the shadow clone jutsu ends, the consciousness of the clone merges with the caster, and so training can be parallelized -- and because Naruto has more chakra than practically anyone else, he can do it the best.

Even better, there's an in-universe reason why everyone doesn't do this: most people can't create more than three or four shadow clones at a time without killing themselves.

Mind you, Naruto Shippuden doesn't exactly promote rational values...