Perhaps a stupid question but, is it so difficult to make a Poser version ?

The work involved for building and a set of materials, yes. Keep in mind you're doing the work twice, and maybe getting less than 1/5 the return. I worked in the spectacle and I had also a company, I learned you can't expect to win every game, but the main thing is to keep your customers !
Today is a day, tomorrow is another day…

There lies the problem. When they no longer buy, they are no longer your customer. However, those people have been replaced with DS customers, enough so that it makes up the difference when that support is dropped. I think that's the part people don't understand. One PA put it best: basically he said when a PA has to support Iray, 3delight and Poser, that becomes unsustainable as far as support. So the weakest link was dropped. Hopefully .duf support can be ramped up for Carrara, but I would not hope to see an increase in Poser files from PAs when they are making money from products that no longer support that platform. You can debate all you like, but the reality now is if you want to get products into carrara, you'll most likely have to install DS and export.