I wouldn't say ego really.. My personal guess is that at a meeting someone said "but do we want to do something that might help another company" and the answer was "no" so they refused the offer. Which is ironic really when you think about it because Daz very much wanted (and I suspect expected) to be inclusive with Genesis and Poser. After that they felt sort of locked into a less than ideal stance. I think at the time they did see content for poser users as very important and for Daz content is still the most important factor as a company. Other wise they would never have worked on a system to try and get the figures into Poser. That choice really did start a change in the landscape for product support. Non inclusion of the Daz figures made everyone start looking at the numbers as far as sales and support. Had Poser included Genesis then I doubt that ever would have happened for many content creators. It would have been (and I think Daz felt very much it would be) a win win for both companies. Daz continues to be able to support poser customers more fully and SM would have had solid content that was well supported and taking much of the stress off of them as far as figure creation goes. SM would also have been able to coat tail on a fair bit of Daz marketing as well. There is a reason companies that might seem competitive work together. It can often be beneficial to everyone. One example would be Daz and Unity. They both sell content but Unity also understands that more content for their customers to use helps potentially expand the customer base.

www.Calida3d.com
Daz studio and Poser content creators