The title pretty much sums it up. Why didn't they. The Systems are rather similar. Earn XPs raise levels, gain and advance Talents and Skills. It's not too difficult too imagine a 4th level arbitrator, with class skills, weapon specialisation (autoshotgun), that will change at the 8th level into the interrogator prestige class, right? It's not that I think the d20 System might be superior, it's just so similar, that I wonder, why they did the work again?