Look, you speaking as if you are talking for the whole comic community. Marvel wouldn't have given Jubilee her own comic series if they didn't think it will do well. They must have receive mails and stuff from fans requesting it, if they think they could do another Spider-Girl hit based on those request, then why shouldn't they? Like you said, the market is different, may be readers or new readers want comics like Jubilee and Spider-Girl. Do you collect Spider-Girl comics or comics like it? You obviously aren't one the audience they are aiming at with the comic.
Comics used to be black and white in the golden years, then they start to become gray, then comes the angst. Now the market seems to be shifting again.