I spoke with one vendor on an unrelated matter, and they pointed out to me that their Poser products were not selling nearly as well as their Daz Studio products.  The vendors are going where the customers are willing to pay to go.

I don't know why the Daz Studio products look better than the Poser-compatible products, but I can usually tell which is which just by looking at the images before reading the ad copy.

I don't know if Poser 13 will be able to use Daz products again or not, but I think such compatibility might address the current disparity between the two.  If compatibility isn't the issue, then I don't know what can be done to close the gap.  I only know that I don't want to stop using Poser, but if the vendors can't get people to buy Poser-compatible products, then I may have to go where the vendors are going, if I want new items in my Runtime.