I think, Catlady, it's because the trad publishers extoll the virtues of trad publishing, and their value added, but when looked at it, there really isn't that much value added given how much you're signing away. When a trad publisher won't put "true and accurate" accounting in their contract, that's a big signal that there's something fishy going on. Also, from everything I've read, the big value added is editorial input and marketing... and these days unless you're a Big Name Author, you don't get much marketing at all, and even editorial input - even as basic as copyediting - is going way down too.
If a trad publisher isn't going to provide marketing, or editorial input, you've got to ask yourself what value are they adding? it sounds like more and more authors are saying "not much."