How come kids on tv shows aren't famous famous?

like extremely famous? i mean mackenzie rosman (7th heaven) marykate and ashley, alexis bledel(gilmore girls) or drake and josh etc. aren't in magazines,like manily preteen magaizines (j-14). and some of them are better and prettier actors, but yet miley cyrus, raven, zach and cody, etc get all talked about. i know the olsen were real famous younger, but i never remember reading about them in magz, just brit, christ, bsb, etc. there are a lot of kid actors dakota and abigail that are on tv shows and movies, yet all the hype goes to disney. what's up with that?