Wizards of the Coast spent lots of time in meetings with Bioware to make sure every damn detail of D&D 3e was implemented according to the book. And even longer time micromanaging the campaign design. A lot of the scenarios are essentially repeats of the others - “do these four smaller thingies and then go kick the main baddie” - because getting that approved by WotC was easier.

Why are there so few D&D games these days? Why do video game dev houses want to make their own RPG systems instead? Well, they don’t want the headache of dealing with WotC.