Daz can't do Poser weight mapping, it can't read any of it's fancy shader node stuff (ever try to use either of the Poser versions of Terradome in Studio? Good luck), and it can't inject PMD files.... just to name a few off the top of my head.
It's a lot easier for a Poser user to make things for DS as DS is free, but for a DS user to invest in Poser, only to not see any real financial gains, just isn't worth it. Daz PAs have said multiple times that they don't see enough extra sales to make including Poser content worth it anymore. For example, and these numbers are an exaggeration, not solid numbers, say a DS only set sells 100 times, that same set even with Poser compatibility may only sell 120 times, making it not worth the effort.
People have chosen to speak with their wallets over there, but aren't happy with the results. They want Poser compatibility, but not enough people buy the stuff when it does exist to make it worth it.
It's becomes a self fulfilling prophecy.
DAZ went DAZ only with only a few products being offered for Poser. Just look at the splash screens. All the products look fantastic. However, almost all new products are not Poser ready.
Poser people see there isn't anything for them.
Poser people stop showing up.
DAZ PA's see the same set for Poser isn't selling by ten to one (And exaggeration, not solid numbers) and say, "See? Poser stuff didn't sale."
This ignores the fact that when DAZ wasn't making "DAZ Only" items and figures, Poser users comprised at least half or more of their sales base. You have to look at the way it was when Poser users were courted just as fervently as DAZ users. Some people switched to DAZ as they company wanted. A lot of people didn't. I am one of them. I belonged to the PC club and only left when I felt abandoned. Here is a basic fact about sales and customers.
It is four times as hard to regain a customer once lost then to keep one. Basic rule. Keep every customer you can.
It's been stated that's easier for a Poser user to make things for DAZ because DS is free. I'm still learning but I would think the effort would be the same to create for both products. but thanks to the factors above, the pool of people buying for Poser at that same location is way down thus you don't get the same financial gain. I still don't hate DAZ. When they put the same effort into bringing me back, I will return. When they make it worth it for a Poser user to join the PC club I will join. In the meantime, Rendo, Xurge, the Hive will have the attention of my wallet.