In Japan, lots of mature people are keen on comics as well as--or more than--children. It is regarded as one of the characteristics of Japanese. Japanese is more childish than others? Comics are children’s amusement? I don’t think so. In Japan, we have a big market “Mature-comics”. There are many comics that are made for adults. They take up various themes, from a love affair to child abuse, from serious problems to comedies. The situation is very similar to Hollywood movies. Japanese case (comics) is quite handicraft-like, though. Many Americans love movies, but it doesn’t mean they are childish, even if they love “Batman”, does it?
The major reason we have such kind of manga is that the pioneers of Japanese comic artists were deeply influenced by foreign movies (Especially American movies). For them, Manga should have been in the same field as movies’. They thought that it wasn’t only comical and satire, it could be more dramatic and touching. They tried to create a work which would be better than movies. If they had lots of money, they might have made a film. But they didn’t, and as you know, you can make manga with paper and a pen. They presented many great works which gave a deep impression to readers in those days. As a result, many talented youths became to Comic artists, and they created more great works again and again… incidentally, it is said that’s one of the reasons the Japanese movie world can’t get very many talented people.
And of course we can’t ignore the effort of the publishers. Now, not a few children prefer video games to comics, and the birthrate has been dropping. It is very important for publishers and even artists to expand the market of comics. Some people predict we’ll have a new genre “the aged comic” in the future. (“The love affair in old-aged home”, for instance.). I can’t--won’t imagine that, but it will be possible, maybe.
In short, I don’t think it is bad that many Japanese love comics. But I think it isn’t so good that many (some?…I hope so) Japanese don’t read novels very much. But such people will go to movies or watch TV shows, if they didn’t have any comics. Because they dislike reading. This is a social problem, but you shouldn’t blame comics for that.