It's a creative problem. At one time, it was difficult for writers and artists to claim ownership of their product, because everything was work for hire. So in the bad old days, when publishers owned everything and creators got nothing--dying in poverty while the publishers made millions off what they created (see Bill Finger)--there were lots of new concepts being created all the time.
But this was clearly a system of exploitation that could not persist. People like Neal Adams fought for creative rights and they won (to some degree) in the late 1970s. Jenette Kahn offered creatives better treatment, which lured many from Marvel and later from Britain, to the Distinguished Competition. Now talent had a share in what they created.
However, if you create a product and you have the potential of making all the money for yourself, when you own it outright, that's a better deal than if the publisher owns a large share of your product. Utlimately, it seems like creators and publishers have gone their separate ways on this matter. Publishers realize that if they just use stuff that was created for them in the bad old days, then they own 100% and they don't have to share (well maybe they have to give some royalties, but only a fraction of their profits). And the creators realize that it's not worth giving up their best ideas to the publishers, when they only get a portion of the profits.
The chances of a creator striking it rich as an independent are very small--but when they do strike it rich the rewards can be great.