I started to watch anime because it happened to be on after Futurama during the Adult Swim block on Cartoon Network. I was impressed with what I saw in some series (Full Metal Alchemist and Paranoia Agent) and started seeking out more of it on my own. Some anime is as good or better than any independent cinema you can find. There's some really unique stuff and just a lot of really good and interesting storytelling. You can develop a lot more depth in ten hours of content than you can in two hours and some anime takes advantage of this fact.
Anime is shown during primetime on major television networks in Japan. Manga is read by just about everyone in Japan. Forty percent of the books published in Japan are manga. There are tons of educational manga like the one reviewed in this post. Given the wide viewership and readership in Japan, a considerable range of manga and anime are created.
Illustrated books and animation are just two other art forms. Most Americans can't get past their limited use in the US. Too bad for them.