Because Japan considers anime to be a subset of film, whereas we in American culture consider animation to be a childish plaything incapable of telling serious stories, presenting impacting issues, or developing meaningful characters. It's a terrible, ignorant idea that is the prevailing approach to animation in our culture.
Japan understands otherwise. Their animated works are, by and large, better than their live-action ones, and those who appreciate anime have come to understand the storytelling potential that animation has, however untapped and misunderstood it may be by most of our own culture.
Gurran Laggan, by the way, is an intentional self-parody of the sci-fi mech genre. Don't look to it for serious storytelling. Naruto actually has an incredibly complex culture, mythos, and story, but it must be watched from the beginning to get it, which unfortunately subjects the viewer to a lot of unnecessary juvenile drivel on the way to the brilliance the show exhibits later. Code Geass I haven't seen, so no comment.
Did you watch the first episodes of these shows? Most anime is not like the episodic drivel that populates western animation; you watch it from the beginning or you will be lost. Thus, if you did not see the beginnings, your ideas are entirely invalid due to lack of context and understanding.