Pretty much the one of the same reasons why people new to Japanese Anime will think that just because it is a cartoon animation with characters with big cutesy eyes (In Pokemon's case, wierd and cute creatures) that it is only for children, well it's not! If you actually get to know the topic at hand, as mentioned before, you will find there is a lot of depth in there and it is a much bigger world than you realise.
I think anyone over the age of 16 Playing pokemon will have a fair understanding that their is more to Anime than pokemon .
I really like Studio Ghibli stuff